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TRF7970A

SLOS743K –AUGUST 2011–REVISED APRIL 2014

TRF7970A Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication

(NFC) Transceiver IC

1 Device Overview

1.1 Features

• Supports Near Field Communication (NFC) • Programmable Output Power: +20 dBm (100 mW),

Standards NFCIP-1 (ISO/IEC 18092) and NFCIP‑2 +23 dBm (200 mW)

(ISO/IEC 21481) • Programmable I/O Voltage Levels From 1.8 VDC

• Completely Integrated Protocol Handling for to 5.5 VDC

ISO15693, ISO18000-3, ISO14443A/B, and • Programmable System Clock Frequency Output

FeliCa™ (RF, RF/2, RF/4) from 13.56-MHz or 27.12-MHz

• Integrated Encoders, Decoders, and Data Framing Crystal or Oscillator

for NFC Initiator, Active and Passive Target • Integrated Voltage Regulator Output for Other

Operation for All Three Bit Rates (106 kbps, System Components (MCU, Peripherals,

212 kbps, 424 kbps) and Card Emulation Indicators), 20 mA (Max)

• RF Field Detector With Programmable Wake-Up • Programmable Modulation Depth

Levels for NFC Passive Transponder Emulation • Dual Receiver Architecture With RSSI for

Operation Elimination of "Read Holes" and Adjacent Reader

• RF Field Detector for NFC Physical Collision System or Ambient In-Band Noise Detection

Avoidance. • Programmable Power Modes for Ultra Low-Power

• Integrated State Machine for ISO14443A System Design (Power Down <1 µA)

Anticollision (Broken Bytes) Operation • Parallel or SPI Interface (With 127-Byte FIFO)

(Transponder Emulation or NFC Passive Target) • Temperature Range: –40°C to 110°C

• Input Voltage Range: 2.7 VDC to 5.5 VDC • 32-Pin QFN Package (5 mm x 5 mm)

1.2 Applications

• Mobile Devices (Tablets, Handsets) • Short-Range Wireless Communication Tasks

(Firmware Updates)

• Secure Pairing ( Bluetooth®, Wi-Fi®, Other Paired

Wireless Networks) • Product Identification or Authentication

• Public Transport or Event Ticketing • Medical Equipment or Consumables

• Passport or Payment (POS) Reader Systems • Access Control, Digital Door Locks

• Sharing of Electronic Business Cards

1.3 Description

The TRF7970A device is an integrated analog front end and data-framing device for a 13.56-MHz RFID

and Near Field Communication (NFC) system. Built-in programming options make the device suitable for a

wide range of applications for proximity and vicinity identification systems.

The device can perform in one of three modes: RFID and NFC reader, NFC peer, or in card emulation

mode. Built-in user-configurable programming options make the device suitable for a wide range of

applications. The TRF7970A device is configured by selecting the desired protocol in the control registers.

Direct access to all control registers allows fine tuning of various reader parameters as needed.

Documentation, reference designs, EVM, and source code TI MSP430™ MCUs or ARM®MCUs are

available.

Device Information

PART NUMBER PACKAGE BODY SIZE

TRF7970ARHB VQFN (32) 5 mm x 5 mm

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

MUX

RX_IN1

RX_IN2

PHASE&

AMPLITUDE

DETECTOR

GAIN RSSI

(AUX)

LOGIC

LEVEL SHIFTER

STATE

CONTROL

LOGIC

[CONTROL

REGISTERS &

COMMAND

LOGIC]

127-BYTE

FIFO

MCU

INTERFACE

VDD_I/O

I/O_0

I/O_1

I/O_2

I/O_3

I/O_4

I/O_5

I/O_6

I/O_7

IRQ

SYS_CLK

DATA _CLK

ISO

PROTOCOL

HANDLING DECODER

RSSI

(EXTERNAL)

PHASE&

AMPLITUDE

DETECTOR

GAIN

RSSI

(MAIN)

FILTER

& AGC DIGITIZER

BIT

FRAMING

SERIAL

CONVERSION

CRC & PARITY

TRANSMITTER ANALOG

FRONT END

TX_OUT

VDD_PA

VSS_PA

DIGITAL CONTROL

STATE MACHINE

CRYSTAL OR OSCILLATOR

TIMING SYSTEM

EN2

ASK/OOK

MOD

OSC_IN

OSC_OUT

VOLTAGE SUPPLY REGULATOR SYSTEMS

(SUPPLY REGULATORS AND REFERENCE VOLTAGES)

VSS_A

VSS_RF

VDD_RF

VDD_X

VSS_D

VSS

VIN

VDD_A

BAND_GAP

RF LEVEL

DETECTOR

TRF7970A

SLOS743K –AUGUST 2011–REVISED APRIL 2014

www.ti.com

1.4 Functional Block Diagram

Figure 1-1 shows the block diagram.

Figure 1-1. Block Diagram

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SLOS743K –AUGUST 2011–REVISED APRIL 2014

Table of Contents

1 Device Overview ......................................... 16.8 Transmitter – Digital Section ........................ 28

6.9 Transmitter – External Power Amplifier and

1.1 Features .............................................. 1Subcarrier Detector ................................. 29

1.2 Applications........................................... 16.10 TRF7970A IC Communication Interface ............ 30

1.3 Description............................................ 16.11 Special Direct Mode for Improved MIFARE™

1.4 Functional Block Diagram ............................ 2Compatibility......................................... 48

2 Revision History ......................................... 46.12 NFC Modes.......................................... 48

3 Device Characteristics.................................. 56.13 Direct Commands from MCU to Reader ............ 51

4 Terminal Configuration and Functions.............. 66.14 Register Description................................. 55

4.1 Pin Assignments...................................... 67 Application Schematic and Layout

4.2 Terminal Functions ................................... 7Considerations.......................................... 75

5 Specifications ............................................ 97.1 TRF7970A Reader System Using Parallel

Microcontroller Interface............................. 75

5.1 Absolute Maximum Ratings .......................... 9

7.2 TRF7970A Reader System Using SPI With SS

5.2 Recommended Operating Conditions ................ 9Mode ................................................ 76

5.3 Electrical Characteristics............................ 10 7.3 Layout Considerations .............................. 77

5.4 Handling Ratings.................................... 11 7.4 Impedance Matching TX_Out (Pin 5) to 50 Ω...... 77

5.5 Thermal Characteristics............................. 11 7.5 Reader Antenna Design Guidelines ................ 79

5.6 Switching Characteristics ........................... 11 8 Device and Documentation Support ............... 80

6 Detailed Description ................................... 12 8.1 Documentation Support ............................. 80

6.1 Overview ............................................ 12 8.2 Community Resources.............................. 80

6.2 System Block Diagram.............................. 15 8.3 Trademarks.......................................... 80

6.3 Power Supplies...................................... 15 8.4 Electrostatic Discharge Caution..................... 80

6.4 Receiver – Analog Section .......................... 21 8.5 Glossary ............................................. 80

6.5 Receiver – Digital Section........................... 22 9 Mechanical Packaging and Orderable

6.6 Oscillator Section ................................... 27 Information .............................................. 80

6.7 Transmitter – Analog Section ....................... 28 9.1 Packaging Information .............................. 80

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SLOS743K –AUGUST 2011–REVISED APRIL 2014

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2 Revision History

NOTE: Page numbers for previous revisions may differ from page numbers in the current version.

Changes from Revision J (February 2014) to Revision K Page

• Changed Figure 1-1 to show 127-byte FIFO...................................................................................... 2

• Moved Section 3 ...................................................................................................................... 5

• Changed title of Section 4 .......................................................................................................... 6

• Changed title of Section 5 ........................................................................................................... 9

• Added ASK/OOK and MOD to VIL and VIH ........................................................................................ 9

• Moved Section 5.3 .................................................................................................................. 10

• Changed VDD_A TYP value from 3.5 V to 3.4 V ................................................................................. 10

• Moved Section 5.4 .................................................................................................................. 11

• Added V(ESD) MIN values, test specifications, and notes....................................................................... 11

• Changed title of Section 5.5 from Dissipation Ratings to Thermal Characteristics......................................... 11

• Moved Section 5.6 .................................................................................................................. 11

• Changed title of Section 6.......................................................................................................... 12

• Moved previous Section 3, Device Overview, to Section 6.1.................................................................. 12

• Changed from "By default, the AGC is frozen after..." to "By default, the AGC window comparator is set after..." ... 21

• Changed from "TX Pulse Length Control register (0x05)" to "TX Pulse Length Control register (0x06)" ............... 28

• Changed from "18.8 s" to "18.8 µs" in the sentence that starts with "If the register contains all zeros..."............... 28

• Changed Table 6-18 to match Table 6-43 ....................................................................................... 50

• Changed command 0x18 to "Test internal RF" ................................................................................. 51

• Changed command 0x19 to "Test external RF" ................................................................................ 51

• Moved Section 6.14................................................................................................................. 55

• Changed the sentence that starts "The AGC action is fast..." from "finishes after four subcarrier pulses" to

"finishes within eight subcarrier pulses" ......................................................................................... 64

• Moved Section 7..................................................................................................................... 75

• Deleted previous Section 10, System Design, and moved contents to Section 7.3 through Section 7.5 ............... 77

• Removed references to figure numbers in Figure 7-3.......................................................................... 78

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SLOS743K –AUGUST 2011–REVISED APRIL 2014

3 Device Characteristics

Table 3-1 shows the supported modes of operation for the TRF7970A device.

Table 3-1. Supported Modes of Operation

P2P Initiator or Reader/Writer Card Emulation P2P Target

Bit rate Bit rate Bit rate

Technology Technology Technology

(kbps) (kbps) (kbps)

106, 212, 424,

NFC-A/B (ISO14443A/B) NFC-A/B 106 NFC-A 106

848(1)

NFC-F (JIS: X6319-4) 212, 424 N/A N/A NFC-F 212, 424

NFC-V (ISO15693) 6.7, 26.7 N/A N/A N/A N/A

(1) 848 kbps only applies to reader/writer mode.

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VDD_A

VIN

VDD_RF

VDD_PA

TX_OUT

VSS_PA

VSS_RX

RX_IN1

I/0_7

RX_IN2

VSS

ASK/OOK

IRQ

MOD

VSS_A

VDD_I/O

Pad

VDD_X

OSC_IN

OSC_OUT

VSS_D

SYS_CLK

DATA_CLK

EN2

9 10 11 12 13 14 15 16

32 31 30 29 28 27 26 25

I/0_6

I/0_5

I/0_4

I/0_3

I/0_2

I/0_1

I/0_0

TRF7970A

SLOS743K –AUGUST 2011–REVISED APRIL 2014

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4 Terminal Configuration and Functions

4.1 Pin Assignments

Figure 4-1 shows the pin assignments for the 32-pin RHB package.

Figure 4-1. 32-Pin RHB Package (Top View)

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4.2 Terminal Functions

Table 4-1 describes the signals.

Table 4-1. Terminal Functions

TERMINAL TYPE (1) DESCRIPTION

NAME NO.

VDD_A 1 OUT Internal regulated supply (2.7 V to 3.4 V) for analog circuitry

VIN 2 SUP External supply input to chip (2.7 V to 5.5 V)

VDD_RF 3 OUT Internal regulated supply (2.7 V to 5 V), normally connected to VDD_PA (pin 4)

VDD_PA 4 INP Supply for PA; normally connected externally to VDD_RF (pin 3)

TX_OUT 5 OUT RF output (selectable output power, 100 mW or 200 mW, with VDD = 5 V)

VSS_PA 6 SUP Negative supply for PA; normally connected to circuit ground

VSS_RX 7 SUP Negative supply for RX inputs; normally connected to circuit ground

RX_IN1 8 INP Main RX input

RX_IN2 9 INP Auxiliary RX input

VSS 10 SUP Chip substrate ground

BAND_GAP 11 OUT Bandgap voltage (VBG = 1.6 V); internal analog voltage reference

Selection between ASK and OOK modulation (0 = ASK, 1 = OOK) for Direct Mode 0 or 1.

ASK/OOK 12 BID Can be configured as an output to provide the received analog signal output.

IRQ 13 OUT Interrupt request

INP External data modulation input for Direct Mode 0 or 1

MOD 14 OUT Subcarrier digital data output (see registers 0x1A and 0x1B)

VSS_A 15 SUP Negative supply for internal analog circuits; connected to GND

VDD_I/O 16 INP Supply for I/O communications (1.8 V to VIN) level shifter. VIN should be never exceeded.

I/O_0 17 BID I/O pin for parallel communication

I/O_1 18 BID I/O pin for parallel communication

I/O pin for parallel communication

I/O_2 19 BID TX Enable (in Special Direct Mode)

I/O pin for parallel communication

I/O_3 20 BID TX Data (in Special Direct Mode)

I/O pin for parallel communication

I/O_4 21 BID Slave Select signal in SPI mode

I/O pin for parallel communication

I/O_5 22 BID Data clock output in Direct Mode 1 and Special Direct Mode

I/O pin for parallel communication

I/O_6 23 BID MISO for serial communication (SPI)

Serial bit data output in Direct Mode 1 or subcarrier signal in Direct Mode 0

I/O pin for parallel communication.

I/O_7 24 BID MOSI for serial communication (SPI)

Selection of power down mode. If EN2 is connected to VIN, then VDD_X is active during power

EN2 25 INP down mode 2 (for example, to supply the MCU).

DATA_CLK 26 INP Data Clock input for MCU communication (parallel and serial)

If EN = 1 (EN2 = don't care) the system clock for MCU is configured. Depending on the crystal

that is used, options are as follows (see register 0x09):

SYS_CLK 27 OUT 13.56-MHz crystal: Off, 3.39 MHz, 6.78 MHz, or 13.56 MHz

27.12-MHz crystal: Off, 6.78 MHz, 13.56 MHz, or 27.12 MHz

If EN = 0 and EN2 = 1, then system clock is set to 60 kHz

EN 28 INP Chip enable input (If EN = 0, then chip is in sleep or power-down mode).

VSS_D 29 SUP Negative supply for internal digital circuits

(1) SUP = Supply, INP = Input, BID = Bidirectional, OUT = Output

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Table 4-1. Terminal Functions (continued)

TERMINAL TYPE (1) DESCRIPTION

NAME NO.

OSC_OUT 30 OUT Crystal or oscillator output

INP Crystal or oscillator input

OSC_IN 31 OUT Crystal oscillator output

Internally regulated supply (2.7 V to 3.4 V) for digital circuit and external devices (for example,

VDD_X 32 OUT MCU)

Thermal Pad PAD SUP Chip substrate ground

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5 Specifications

5.1 Absolute Maximum Ratings (1) (2)

over operating free-air temperature range (unless otherwise noted)

VIN Input voltage range -0.3 V to 6 V

IIN Maximum current VIN 150 mA

Any condition 140°C

TJMaximum operating virtual junction temperature Continuous operation, long-term reliability (3) 125°C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only and functional operation of the device at these or any other conditions beyond those indicated under Operating Conditions are not

implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) All voltage values are with respect to substrate ground terminal VSS.

(3) The maximum junction temperature for continuous operation is limited by package constraints. Operation above this temperature may

result in reduced reliability or lifetime of the device.

5.2 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)

MIN TYP MAX UNIT

VIN Operating input voltage 2.7 5 5.5 V

TAOperating ambient temperature -40 25 110 °C

TJOperating virtual junction temperature -40 25 125 °C

I/O lines, IRQ, SYS_CLK, DATA_CLK, 0.2 x

VIL Input voltage - logic low V

EN, EN2, ASK/OOK, MOD VDD_I/O

I/O lines, IRQ, SYS_CLK, DATA_CLK, 0.8 x

VIH Input voltage threshold, logic high V

EN, EN2, ASK/OOK, MOD VDD_I/O

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5.3 Electrical Characteristics

TYP operating conditions are TA= 25°C, VIN = 5 V, full-power mode (unless otherwise noted)

MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

All building blocks disabled, including supply-

IPD1 Supply current in Power Down Mode 1 voltage regulators; measured after 500-ms 0.5 5 µA

settling time (EN = 0, EN2 = 0)

The SYS_CLK generator and VDD_X remain

Supply current in Power Down Mode 2

IPD2 active to support external circuitry; measured 120 200 µA

(Sleep Mode) after 100-ms settling time (EN = 0, EN2 = 1)

Oscillator running, supply-voltage regulators in

ISTBY Supply current in stand-by mode 1.9 3.5 mA

low-consumption mode (EN = 1, EN2 = x)

Supply current without antenna driver Oscillator, regulators, RX and AGC active, TX

ION1 10.5 14 mA

current is off

Oscillator, regulators, RX and AGC and TX

ION2 Supply current – TX (half power) 70 78 mA

active, POUT = 100 mW

Oscillator, regulators, RX and AGC and TX

ION3 Supply current – TX (full power) 130 150 mA

active, POUT = 200 mW

VPOR Power-on reset voltage Input voltage at VIN 1.4 2 2.6 V

VBG Bandgap voltage (pin 11) Internal analog reference voltage 1.5 1.6 1.7 V

Regulated output voltage for analog

VDD_A VIN = 5 V 3.1 3.4 3.8 V

circuitry (pin 1)

VDD_X Regulated supply for external circuitry Output voltage pin 32, VIN = 5 V 3.1 3.4 3.8 V

IVDD_Xmax Maximum output current of VDD_X Output current pin 32, VIN = 5 V 20 mA

Half-power mode, VIN = 2.7 V to 5.5 V 8 12

RRFOUT Antenna driver output resistance (1) Ω

Full-power mode, VIN = 2.7 V to 5.5 V 4 6

RRFIN RX_IN1 and RX_IN2 input resistance 4 10 20 kΩ

Maximum RF input voltage at RX_IN1 and

VRF_INmax VRF_INmax should not exceed VIN 3.5 Vpp

RX_IN2

fSUBCARRIER= 424 kHz 1.4 2.5

Minimum RF input voltage at RX_IN1 and

VRF_INmin mVpp

RX_IN2 (input sensitivity)(2) fSUBCARRIER = 848 kHz 2.1 3

fSYS_CLK SYS_CLK frequency In power mode 2, EN = 0, EN2 = 1 25 60 120 kHz

fCCarrier frequency Defined by external crystal 13.56 MHz

Time until oscillator stable bit is set (register

tCRYSTAL Crystal run-in time 3 ms

0x0F)(3)

Depends on capacitive load on the I/O lines,

fD_CLKmax Maximum DATA_CLK frequency(4) 2 8 10 MHz

recommendation is 2 MHz(4)

ROUT Output resistance I/O_0 to I/O_7 500 800 Ω

RSYS_CLK Output resistance RSYS_CLK 200 400 Ω

(1) Antenna driver output resistance

(2) Measured with subcarrier signal at RX_IN1 or RX_IN2 and measured the digital output at MOD pin with register 0x1A bit 6 = 1.

(3) Depends on the crystal parameters and components

(4) Recommended DATA_CLK speed is 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not

exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output

resistance of 400 Ω(12-ns time constant when 30-pF load used).

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5.4 Handling Ratings

MIN MAX UNIT

TSTG Storage temperature range -55 150 °C

V(ESD) Electrostatic discharge Human-Body Model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) -2 2 kV

Charged-Device Model (CDM), per JEDEC specification JESD22-C101, -500 500 V

all pins(2)

Machine Model (MM) -200 200 V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Pins listed as 2 kV

may actually have higher performance.

(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Pins listed as 500 V

may actually have higher performance.

5.5 Thermal Characteristics

POWER RATING(2)

PACKAGE θJC θJA(1)

TA≤25°C TA≤85°C

RHB (32 pin) 31°C/W 36.4°C/W 2.7 W 1.1 W

(1) This data was taken using the JEDEC standard high-K test PCB.

(2) Power rating is determined with a junction temperature of 125°C. This is the point where distortion starts to increase substantially.

Thermal management of the final PCB should strive to keep the junction temperature at or below 125°C for best performance and long-

term reliability.

5.6 Switching Characteristics

TYP operating conditions are TA= 25°C, VIN = 5 V, full-power mode (unless otherwise noted)

MIN and MAX operating conditions are over recommended ranges of supply voltage and operating free-air temperature

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

DATA_CLK time high or low, one half of

tLO/HI Depends on capacitive load on the I/O lines(1) 250 62.5 50 ns

DATA_CLK at 50% duty cycle

Slave select lead time, slave select low to

tSTE,LEAD 200 ns

clock

Slave select lag time, last clock to slave

tSTE,LAG 200 ns

select high

Slave select disable time, slave select

tSTE,DIS rising edge to next slave select falling 300 ns

edge

tSU,SI MOSI input data setup time 15 ns

tHD,SI MOSI input data hold time 15 ns

tSU,SO MISO input data setup time 15 ns

tHD,SO MISO input data hold time 15 ns

tVALID,SO MISO output data valid time DATA_CLK edge to MISO valid, CL≤30 pF 30 50 75 ns

(1) Recommended DATA_CLK speed is 2 MHz. Higher data clock depends on the capacitive load. Maximum SPI clock speed should not

exceed 10 MHz. This clock speed is acceptable only when external capacitive load is less than 30 pF. MISO driver has a typical output

resistance of 400 Ω(12-ns time constant when 30-pF load used).

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TRF7970A MCU

(MSP430/ARM)

Matching

VDD_X VDD_I/O

TX_OUT

RX_IN 1

RX_IN2 VSS VIN

Parallel

or SPI

Supply: 2.7 V – 5.5 V

VDD

Crystal

13.56 MHz

XIN

TRF7970A

SLOS743K –AUGUST 2011–REVISED APRIL 2014

www.ti.com

6 Detailed Description

6.1 Overview

6.1.1 RFID and NFC Operation – Reader and Writer

The TRF7970A is a high performance 13.56-MHz HF RFID and NFC Transceiver IC composed of an

integrated analog front end (AFE) and a built-in data framing engine for ISO15693, ISO14443A/B, and

FeliCa. This includes data rates up to 848 kbps for ISO14443 with all framing and synchronization tasks

on board (in default mode). The TRF7970A also supports NFC Tag Type 1, 2, 3, and 4 operations. This

architecture enables the customer to build a complete cost-effective yet high-performance multi-protocol

13.56-MHz RFID and NFC system together with a low-cost microcontroller.

Other standards and even custom protocols can be implemented by using either of the Direct Modes that

the device offers. These Direct Modes (0 and 1) allow the user to fully control the analog front end (AFE)

and also gain access to the raw subcarrier data or the unframed but already ISO formatted data and the

associated (extracted) clock signal.

The receiver system has a dual input receiver architecture. The receivers also include various automatic

and manual gain control options. The received input bandwidth can be selected to cover a broad range of

input subcarrier signal options.

The received signal strength from transponders, ambient sources, or internal levels is available through

the RSSI register. The receiver output is selectable among a digitized subcarrier signal and any of the

integrated subcarrier decoders. The selected subcarrier decoder delivers the data bit stream and the data

clock as outputs.

The TRF7970A also includes a receiver framing engine. This receiver framing engine performs the CRC

or parity check, removes the EOF and SOF settings, and organizes the data in bytes for ISO14443A/B,

ISO15693, and FeliCa protocols. Framed data is then accessible to the microcontroller (MCU) through a

127-byte FIFO register.

Figure 6-1. Application Block Diagram

A parallel or serial interface (SPI) can be used for the communication between the MCU and the

TRF7970A reader. When the built-in hardware encoders and decoders are used, transmit and receive

functions use a 127-byte FIFO register. For direct transmit or receive functions, the encoders and

decoders can be bypassed so that the MCU can process the data in real time. The TRF7970A supports

data communication voltage levels from 1.8 V to 5.5 V for the MCU I/O interface. The transmitter has

selectable output-power levels of 100 mW (+20 dBm) or 200 mW (+23 dBm) equivalent into a 50-Ωload

when using a 5-V supply.

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The transmitter supports OOK and ASK modulation with selectable modulation depth. The TRF7970A also

includes a data transmission engine that comprises low-level encoding for ISO15693, ISO14443A/B and

FeliCa. Included with the transmit data coding is the automatic generation of Start Of Frame (SOF), End

Of Frame (EOF), Cyclic Redundancy Check (CRC), or parity bits.

Several integrated voltage regulators ensure a proper power-supply noise rejection for the complete

reader system. The built-in programmable auxiliary voltage regulator VDD_X (pin 32), is able to deliver up to

20 mA to supply a microcontroller and additional external circuits within the reader system.

6.1.2 NFC Device Operation – Initiator

The desired system of operation (bit rate) is achieved by selecting the option bits in control registers in the

same way as for RFID reader operation. Also the communication to external MCU and data exchange is

identical.

The transmitting system comprises an RF level detector (programmable level) which is used for initial (or

response) RF collision avoidance. The RF collision avoidance sequence is started by sending a direct

command. If successful, the NFC initiator can send the data or commands, the MCU has loaded in the

FIFO register. The coding of this data is done by hardware coders either in ISO14443A/B format or in

FeliCa format. The coders also provide CRC and parity bits (if required) and automatically add preambles,

SOF, EOF, and synchronization bytes as defined by selected protocol.

The receiver system offers same analog features (AGC, AM/PM, bandwidth selection, etc.) as described

previously in RFID and NFC reader and writer description. The system comprises integrated decoders for

passive targets (ISO14443A/B tag or FeliCa) or active targets (ISO14443A/B reader or FeliCa). For all this

options, the system also supports framing including CRC and parity check and removal of SOF, EOF, and

synchronization bytes as specified by the selected protocol.

6.1.3 NFC Device Operation – Target

The desired system of operation (bit rate) is achieved by selecting the option bits in control registers in the

same way as for RFID reader or NFC initiator operation. Also the communication to external MCU and

data exchange is identical.

The activation of NFC target is done when a sufficient RF field level is detected on the antenna. The level

needed for wake-up is selectable and is stored in non-volatile register.

When the activation occurs, the system performs automatic power-up and waits for the first command to

be received. Based on this command, the system knows if it should operate as passive or active target

and at what bit rate. After activation, the receiver system offers the same analog features (for example,

AGC, AM/PM, and bandwidth selection) as in the case of an RFID reader.

When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip

keeps the supply system on. If EN2 = L and EN = L, the chip is in complete power down. To operate as

NFC target or Tag emulator, the MCU must load a value different from zero (0) in Target Detection Level

complete power down and consumes only 3.5 µA). The RF measurement constantly monitors the RF

signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the in

Target Detection Level register, the chip is automatically activated (EN is internally forced high).

When the voltage supply system and the oscillator are started and are stable, osc_ok goes high (B6 of

RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).

Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly

also during normal operation). This informs the MCU that the chip should start operation as NFC TARGET

device. When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set

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in IRQ register. The MCU must set EN = H (confirm the power-up) in the time between the two IRQs,

because the internal power-up ends after the second IRQ. The type and coding of the first initiator (or

reader in the case of a tag emulator) command defines the communication protocol type that the target

must use. Therefore, the communication protocol type is available in the NFC Target Protocol register

immediately after receiving the first command.

Based on the first command from the INITIATOR, the following actions are taken:

• If the first command is SENS_REQ or ALL_REQ the TARGET must enter the SDD protocol for 106-

kbps passive communication to begin; afterward, the baud rate can be changed to 212 kbps or 424

kbps, according to the system requirements. If bit B5 in the NFC Target Detection Level register is not

set, the MCU handles the SDD and the command received is send to FIFO. If the RF field is turned off

(B7 in NFC Target Protocol register is low) at any time, the system sends an IRQ to the MCU with bit

B2 (RF field change) in the IRQ register set high. This informs the MCU that the procedure was

aborted and the system must be reset. The clock extractor is automatically activated in this mode.

• If the command is SENS_REQ or ALL_REQ and the card emulation bit in ISO Control register is set,

the system emulates an ISO14443A/B tag. The procedure does not differ from the one previously

described for the case of a passive target at 106 kbps. The clock extractor is automatically activated in

this mode. To emulate a FeliCa card, the ISO Control register must be set for passive target mode at

either 212 kbps or 424 kbps.

• If the first command is a POLLING request, the system becomes the TARGET in passive

communication using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU

directly. The POLLING response is sent in one of the slots automatically calculated by the MCU (first

slot starts 2.416 ms after end of command, and slots follow in 1.208 ms).

• If the first command is ATR_REQ, the system operates as an active TARGET using the same

communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled

by MCU. The chip is only required to time the response collision avoidance, which is done on direct

command from MCU. When the RF field is switched on and the minimum wait time is elapsed, the chip

sends an IRQ with B1 (RF collision avoidance finished) set high. This signals the MCU that it can send

the reply.

• If the first command is coded as ISO14443B and the Tag emulation bit is set in the ISO Control

MCU, and the chip provides all physical level coding, decoding, and framing for this protocol.

6.1.3.1 Active Target

If the first command received by the RF interface defines the system as an active target, then the receiver

selects the appropriate data decoders (ISO14443A\B reader or FeliCa) and framing option. Only the raw

(decoded) data is forwarded to the MCU through the FIFO. SOF, EOF, preamble, sync bytes, CRC, and

parity bytes are checked by the framer and discarded.

The transmitting system includes an RF level detector (programmable level) that is used for RF collision

avoidance. The RF collision avoidance sequence is started by sending a direct command. If successful,

the NFC initiator can send the data that the MCU has loaded in the FIFO register. The coding of this data

is done by hardware coders either in ISO14443A format (106-kbps system) or in FeliCa format for (212-

kbps and 424-kbps systems). The coders also provide CRC and parity bits (if required) and automatically

add preambles, SOF, EOF, and synchronization bytes as defined by selected protocol.

6.1.3.2 Passive Target

If the first command received by the RF interface defines the system as a passive target, then the receiver

selects the appropriate data decoders (ISO14443A\B reader or FeliCa) and framing option. Again, only the

raw (decoded) data is forwarded to the MCU through the FIFO; SOF, EOF, preamble, sync bytes, CRC,

and parity bytes are checked by the framer and discarded. The receiver works same as in the case of an

active target.

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MUX

RX_IN1

RX_IN2

PHASE&

AMPLITUDE

DETECTOR

GAIN RSSI

(AUX)

LOGIC

LEVEL SHIFTER

STATE

CONTROL

LOGIC

[CONTROL

REGISTERS &

COMMAND

LOGIC]

127-BYTE

FIFO

MCU

INTERFACE

VDD_I/O

I/O_0

I/O_1

I/O_2

I/O_3

I/O_4

I/O_5

I/O_6

I/O_7

IRQ

SYS_CLK

DATA _CLK

ISO

PROTOCOL

HANDLING DECODER

RSSI

(EXTERNAL)

PHASE&

AMPLITUDE

DETECTOR

GAIN

RSSI

(MAIN)

FILTER

& AGC DIGITIZER

BIT

FRAMING

SERIAL

CONVERSION

CRC & PARITY

TRANSMITTER ANALOG

FRONT END

TX_OUT

VDD_PA

VSS_PA

DIGITAL CONTROL

STATE MACHINE

CRYSTAL OR OSCILLATOR

TIMING SYSTEM

EN2

ASK/OOK

MOD

OSC_IN

OSC_OUT

VOLTAGE SUPPLY REGULATOR SYSTEMS

(SUPPLY REGULATORS AND REFERENCE VOLTAGES)

VSS_A

VSS_RF

VDD_RF

VDD_X

VSS_D

VSS

VIN

VDD_A

BAND_GAP

RF LEVEL

DETECTOR

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The transmit system in passive target mode differs from active target and operates similar to the standard

tag. There is no automatic RF collision avoidance sequence, and encoders are used to code the data for

ISO14443A\B tag (at 106 kbps, to start) or FeliCa (at 212 kbps, to start) format. The collision avoidance

must be handled by the firmware on the connected MCU. The coding system adds all of the SOF, EOF,

CRC, parity bits, and synchronization bytes that are required by protocol. On the physical level, the

modulation of the initiator's RF field is done by changing the termination impedance of the antenna

between 4 Ωand open.

6.1.3.3 Card Emulation

The chip can enter this mode by setting appropriate option bits. There are two options to emulate a card.

For ISO14443A\B, the emulation supports 106-kbps data rate to start. For ISO14443A, the anticollision

algorithm can be performed using an internal state machine, which relieves the MCU of any real-time

tasks. The unique ID required for anticollision is provided by the MCU after wake-up of the system.

6.2 System Block Diagram

Figure 6-2 shows a block diagram of the TRF7970A.

Figure 6-2. System Block Diagram

6.3 Power Supplies

The TRF7970A positive supply input VIN (pin 2) sources three internal regulators with output voltages

VDD_RF, VDD_A and VDD_X. All regulators use external bypass capacitors for supply noise filtering and must

be connected as indicated in reference schematics. These regulators provide a high power supply reject

ratio (PSRR) as required for RFID reader systems. All regulators are supplied by VIN (pin 2).

The regulators are not independent and have common control bits in register 0x0B for output voltage

setting. The regulators can be configured to operate in either automatic or manual mode (register 0x0B,

bit 7). The automatic regulator setting mode ensures an optimal compromise between PSRR and the

highest possible supply voltage for RF output (to ensure maximum RF power output). The manual mode

allows the user to manually configure the regulator settings.

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6.3.1 Supply Arrangements

Regulator Supply Input: VIN

The positive supply at VIN (pin 2) has an input voltage range of 2.7 V to 5.5 V. VIN provides the supply

input sources for three internal regulators with the output voltages VDD_RF, VDD_A, and VDD_X. External

bypass capacitors for supply noise filtering must be used (per reference schematics).

NOTE

VIN must be the highest voltage supplied to the TRF7970A.

RF Power Amplifier Regulator: VDD_RF

The VDD_RF (pin 3) regulator is supplying the RF power amplifier. The voltage regulator can be set for

either 5-V or 3-V operation. External bypass capacitors for supply noise filtering must be used (per

reference schematics). When configured for 5-V manual-operation, the VDD_RF output voltage can be set

from 4.3 V to 5 V in 100-mV steps. In 3-V manual-operation, the output can be programmed from 2.7 V to

3.4 V in 100-mV steps. The maximum output current capability for 5-V operation is 150 mA and for 3-V

operation is 100 mA.

Analog Supply Regulator: VDD_A

Regulator VDD_A (pin 1) supplies the analog circuits of the device. The output voltage setting depends on

the input voltage and can be set for 5-V and 3-V operation. When configured for 5-V manual-operation,

the output voltage is fixed at 3.4 V. External bypass capacitors for supply noise filtering must be used (per

reference schematics). When configured for 3-V manual-operation, the VDD_A output can be set from 2.7 V

to 3.4 V in 100-mV steps (see Table 6-2).

Note: the configuration of VDD_A and VDD_X regulators are not independent from each other. The VDD_A

output current should not exceed 20 mA.

Digital Supply Regulator: VDD_X

The digital supply regulator VDD_X (pin 32) provides the power for the internal digital building blocks and

can also be used to supply external electronics within the reader system. When configured for 3-V

operation, the output voltage can be set from 2.7 to 3.4 V in 100-mV steps. External bypass capacitors for

supply noise filtering must be used (per reference schematics).

Note: the configuration of the VDD_A and VDD_X regulators are not independent from each other. The VDD_X

output current should not exceed 20 mA.

The RF power amplifier regulator (VDD_RF), analog supply regulator (VDD_A) and digital supply regulator

(VDD_X) can be configured to operate in either automatic or manual mode described in Section 6.3.2. The

automatic regulator setting mode ensures an optimal compromise between PSRR and the highest

possible supply voltage to ensure maximum RF power output.

By default, the regulators are set in automatic regulator setting mode. In this mode, the regulators are

automatically set every time the system is activated by setting EN input High or each time the automatic

regulator setting bit, B7 in register 0x0B is set to a 1. The action is started on the 0 to 1 transition. This

means that, if the user wants to re-run the automatic setting from a state in which the automatic setting bit

is already high, the automatic setting bit (B7 in register 0x0B) should be changed: 1-0-1.

By default, the regulator setting algorithm sets the regulator outputs to a "Delta Voltage" of 250 mV below

VIN, but not higher than 5 V for VDD_RF and 3.4 V for VDD_A and VDD_A. The "Delta Voltage" in automatic

regulator mode can be increased up to 400 mV (for details, see bits B0 to B2 in register 0x0B).

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Power Amplifier Supply: VDD_PA

The power amplifier of the TRF7970A is supplied through VDD_PA(pin 4). The positive supply pin for the RF

power amplifier is externally connected to the regulator output VDD_RF (pin 3).

I/O Level Shifter Supply: VDD_I/O

The TRF7970A has a separate supply input VDD_I/O (pin 16) for the built-in I/O level shifter. The supported

input voltage ranges from 1.8 V to VIN, not exceeding 5.5 V. Pin 16 is used to supply the I/O interface pins

(I/O_0 to I/O_7), IRQ, SYS_CLK, and DATA_CLK pins of the reader. In typical applications, VDD_I/O is

directly connected to VDD_X, while VDD_X also supplies the MCU. This ensures that the I/O signal levels of

the MCU match the logic levels of the TRF7970A.

Negative Supply Connections: VSS, VSS_TX, VSS_RX, VSS_A, VSS_PA

The negative supply connections VSS_X of each functional block are all externally connected to GND.

The substrate connection is VSS (pin 10), the analog negative supply is VSS_A (pin 15), the logic negative

supply is VSS_D (pin 29), the RF output stage negative supply is VSS_PA (pin 6), and the negative supply for

the RF receiver VSS_RX (pin 7).

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6.3.2 Supply Regulator Settings

The input supply voltage mode of the reader needs to be selected. This is done in the Chip Status Control

configuration is 5 V, which reflects an operating supply voltage range of 4.3 V to 5.5 V. If the supply

voltage is below 4.3 V, the 3-V configuration should be used.

The various regulators can be configured to operate in automatic or manual mode. This is done in the

Regulator and I/O Control register (0x0B) as shown in Table 6-1 and Table 6-2.

Table 6-1. Supply Regulator Setting: 5-V System

Address Comments

B7 B6 B5 B4 B3 B2 B1 B0

(hex)

Automatic Mode (default)

0B 1 x x x x x 0 0 Automatic regulator setting 400-mV difference

Manual Mode

0B 0 x x x x 1 1 1 VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 1 1 0 VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 1 0 1 VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 1 0 0 VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 0 1 1 VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 0 1 0 VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 0 0 1 VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 0 0 0 VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V

(1) x = Don't care

Table 6-2. Supply Regulator Setting: 3-V System

Address Comments

B7 B6 B5 B4 B3 B2 B1 B0

(hex)

Automatic Mode (default)

0B 1 x x x x x 0 0 Automatic regulator setting 400-mV difference

Manual Mode

0B 0 x x x x 1 1 1 VDD_RF = 3.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 x x x x 1 1 0 VDD_RF = 3.3 V, VDD_A = 3.3 V, VDD_X = 3.3 V

0B 0 x x x x 1 0 1 VDD_RF = 3.2 V, VDD_A = 3.2 V, VDD_X = 3.2 V

0B 0 x x x x 1 0 0 VDD_RF = 3.1 V, VDD_A = 3.1 V, VDD_X = 3.1 V

0B 0 x x x x 0 1 1 VDD_RF = 3.0 V, VDD_A = 3.0 V, VDD_X = 3.0 V

0B 0 x x x x 0 1 0 VDD_RF = 2.9 V, VDD_A = 2.9 V, VDD_X = 2.9 V

0B 0 x x x x 0 0 1 VDD_RF = 2.8 V, VDD_A = 2.8 V, VDD_X = 2.8 V

0B 0 x x x x 0 0 0 VDD_RF = 2.7 V, VDD_A = 2.7 V, VDD_X = 2.7 V

(1) x = Don't care

The regulator configuration function adjusts the regulator outputs by default to 400 mV below VIN level, but

not higher than 5 V for VDD_RF, 3.4 V for VDD_A and VDD_X. This ensures the highest possible supply

voltage for the RF output stage while maintaining an adequate PSRR (power supply rejection ratio).

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6.3.3 Power Modes

The chip has several power states, which are controlled by two input pins (EN and EN2) and several bits

in the chip status control register (0x00) (see Table 6-3 and Table 6-4).

Table 6-3. 3.3-V Operation Power Modes(1)

Chip Regulator Typical

Status SYS_CLK Typical

Control SYS_CLK Power

Mode EN2 EN Control Transmitter Receiver (13.56 VDD_X Current

(0x0B) (dBm)

(0x00)

Power Down 0 0 XX XX OFF OFF OFF OFF OFF <0.001 -

Sleep Mode 1 0 XX XX OFF OFF OFF ON ON 0.120 -

Standby Mode at X 1 80 00 OFF OFF ON X ON 2 -

+3.3 VDC

Mode 1 at +3.3 VDC X 1 00 00 OFF OFF ON X ON 3 -

Mode 2 at +3.3 VDC X 1 02 00 OFF ON ON X ON 9 -

Mode 3 (Half Power) at X 1 30 07 ON ON ON X ON 53 14.5

+3.3 VDC

Mode 4 (Full Power) at X 1 20 07 ON ON ON X ON 67 17

+3.3 VDC

(1) X = Don't care

Table 6-4. 5-V Operation Power Modes(1)

Chip Regulator Typical

Status SYS_CLK Typical

Control SYS_CLK Power

Mode EN2 EN Control Transmitter Receiver (13.56 VDD_X Current

(0x0B) (dBm)

(0x00)

Power Down 0 0 XX XX OFF OFF OFF OFF OFF <0.001 -

Sleep Mode 1 0 XX XX OFF OFF OFF ON ON 0.120 -

Standby Mode at X 1 81 07 OFF OFF ON X ON 3 -

+5 VDC

Mode 1 at +5 VDC X 1 01 07 OFF OFF ON X ON 5 -

Mode 2 at +5 VDC X 1 03 07 OFF ON ON X ON 10.5 -

Mode 3 (Half Power) at X 1 31 07 ON ON ON X ON 70 20

+5 VDC

Mode 4 (Full Power) at X 1 21 07 ON ON ON X ON 130 23

+5 VDC

(1) X = Don't care

Table 6-3 and Table 6-4 show the configuration for the different power modes when using a 3.3-V or 5-V

system supply, respectively. The main reader enable signal is pin EN. When EN is set high, all of the

reader regulators are enabled, the 13.56-MHz oscillator is running and the SYS_CLK (output clock for

external micro controller) is also available.

The input pin EN2 has two functions:

• A direct connection from EN2 to VIN to ensure the availability of the regulated supply VDD_X and an

auxiliary clock signal (60 kHz, SYS_CLK) for an external MCU. This mode (EN = 0, EN2 = 1) is

intended for systems in which the MCU is also being supplied by the reader supply regulator (VDD_X)

and the MCU clock is supplied by the SYS_CLK output of the reader. This allows the MCU supply and

clock to be available during sleep mode.

• EN2 enables the start-up of the reader system from complete power down (EN = 0, EN2 = 0). In this

case the EN input is being controlled by the MCU (or other system device) that is without supply

voltage during complete power down (thus unable to control the EN input). A rising edge applied to the

EN2 input (which has an approximately 1-V threshold level) starts the reader supply system and 13.56-

MHz oscillator (identical to condition EN = 1).

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VIN

EN2

5 ms

6 ms

VIN

EN2

2 ms

5 ms

6 ms

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When user MCU is controlling EN and EN2, a delay of 1 ms between EN and EN2 must be used. If the

MCU controls only EN, EN2 is recommended to be connected to either VIN or GND, depending on the

application MCU requirements for VDD_X and SYS_CLK.

Figure 6-3. Nominal Start-Up Sequence Using SPI With SS (MCU Controls EN2)

Figure 6-4. Nominal Start-Up Sequence Using Parallel (MCU Controls EN2)

This start-up mode lasts until all of the regulators have settled and the 13.56-MHz oscillator has stabilized.

If the EN input is set high (EN = 1) by the MCU (or other system device), the reader stays active. If the EN

input is not set high (EN = 0) within 100 µs after the SYS_CLK output is switched from auxiliary clock (60

kHz) to high-frequency clock (derived from the crystal oscillator), the reader system returns to complete

Power-Down Mode 1. This option can be used to wake-up the reader system from complete Power Down

(PD Mode 1) by using a pushbutton switch or by sending a single pulse.

After the reader EN line is high, the other power modes are selected by control bits within the chip status

control register (0x00). The power mode options and states are listed in Table 6-3.

When EN is set high (or on rising edge of EN2 and then confirmed by EN = 1) the supply regulators are

activated and the 13.56-MHz oscillator started. When the supplies are settled and the oscillator frequency

is stable, the SYS_CLK output is switched from the auxiliary frequency of 60 kHz to the 13.56-MHz

frequency derived from the crystal oscillator. At this point, the reader is ready to communicate and perform

the required tasks. The MCU can then program the chip status control register 0x00 and select the

operation mode by programming the additional registers.

• Stand-by Mode (bit 7 = 1 of register 0x00), the reader is capable of recovering to full operation in

100 µs.

• Mode 1 (active mode with RF output disabled, bit 5 = 0 and bit 1 = 0 of register 0x00) is a low power

mode which allows the reader to recover to full operation within 25 µs.

• Mode 2 (active mode with only the RF receiver active, bit 1 = 1 of register 0x00) can be used to

measure the external RF field (as described in RSSI measurements paragraph) if reader-to-reader

anticollision is implemented.

• Modes 3 and 4 (active modes with the entire RF section active, bit 5 = 1 of register 0x00) are the

normal modes used for normal transmit and receive operations.

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6.4 Receiver – Analog Section

6.4.1 Main and Auxiliary Receivers

The TRF7970A has two receiver inputs: RX_IN1 (pin 8) and RX_IN2 (pin 9). Each of the input is

connected to an external capacitive voltage divider to ensure that the modulated signal from the tag is

available on at least one of the two inputs. This architecture eliminates any possible communication holes

that may occur from the tag to the reader.

The two RX inputs (RX_IN1 and RX_IN2) are multiplexed into two receivers - the main receiver and the

auxiliary receiver. Only the main receiver is used for reception, the auxiliary receiver is used for signal

quality monitoring. Receiver input multiplexing is controlled by bit B3 in the Chip Status Control register

(address 0x00).

After startup, RX_IN1 is multiplexed to the main receiver which is composed of an RF envelope detection,

first gain and band-pass filtering stage, second gain and filtering stage with AGC. Only the main receiver

is connected to the digitizing stage which output is connected to the digital processing block. The main

receiver also has an RSSI measuring stage, which measures the strength of the demodulated signal

(subcarrier signal).

The primary function of the auxiliary receiver is to monitor the RX signal quality by measuring the RSSI of

the demodulated subcarrier signal (internal RSSI). After startup, RX_IN2 is multiplexed to the auxiliary

receiver. The auxiliary receiver has an RF envelope detection stage, first gain and filtering with AGC stage

and finally the auxiliary RSSI block.

The default MUX setting is RX_IN1 connected to the main receiver and RX_IN2 connected to the auxiliary

receiver. To determine the signal quality, the response from the tag is detected by the "main" (pin RX_IN1)

and "auxiliary" (pin RX_IN2) RSSI. Both values measured and stored in the RSSI level register (address

0x0F). The MCU can read the RSSI values from the TRF7970A RSSI register and make the decision if

swapping the input- signals is preferable or not. Setting B3 in Chip Status Control register (address 0x00)

to 1 connects RX_IN1 (pin 8) to the auxiliary received and RX_IN2 (pin 9) to the main receiver. This

mechanism needs to be used to avoid reading holes.

The main and auxiliary receiver input stages are RF envelope detectors. The RF amplitude at RX_IN1 and

RX_IN2 should be approximately 3 VPP for a VINsupply level greater than 3.3 V. If the VIN level is lower,

the RF input peak-to-peak voltage level should not exceed the VINlevel.

6.4.2 Receiver Gain and Filter Stages

The first gain and filtering stage has a nominal gain of 15 dB with an adjustable band-pass filter. The

band-pass filter has programmable 3d-B corner frequencies between 110 kHz to 450 kHz for the high-

pass filter and 570 kHz to 1500 kHz for the low-pass filter. After the band-pass filter, there is another gain-

and-filtering stage with a nominal gain of 8 dB and with frequency characteristics identical to the first band-

pass stage.

The internal filters are configured automatically depending on the selected ISO communication standard in

the ISO Control register (address 0x01). If required, additional fine tuning can be done by writing directly

to the RX special setting registers (address 0x0A).

The main receiver also has a second receiver gain and digitizer stage which is included in the AGC loop.

The AGC loop is activated by setting the bit B2 = 1 in the Chip Status Control register (0x00). When

activated, the AGC continuously monitors the input signal level. If the signal level is significantly higher

than an internal threshold level, gain reduction is activated.

By default, the AGC window comparator is set after the first 4 pulses of the subcarrier signal. This

prevents the AGC from interfering with the reception of the remaining data packet. In certain situations,

this AGC freeze is not optimal, so it can be removed by setting B0 = 1 in the RX special setting register

(address 0x0A).

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Table 6-5. RX Special Setting Register (0x0A)

Function: Sets the gains and filters directly

Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register 0x01. When bits B7, B6, B5 and B4 are all zero, the

filters are set for ISO14443B (240 kHz to 1.4 MHz).

Bit Name Function Description

B7 C212 Bandpass 110 kHz to 570 kHz Appropriate for 212-kHz subcarrier system (FeliCa)

B6 C424 Bandpass 200 kHz to 900 kHz Appropriate for 424-kHz subcarrier used in ISO15693

Appropriate for Manchester-coded 848-kHz subcarrier used in ISO14443A

B5 M848 Bandpass 450 kHz to 1.5 MHz and B

Bandpass 100 kHz to 1.5 MHz

B4 hbt Appropriate for highest bit rate (848 kbps) used in high-bit-rate ISO14443

Gain reduced for 18 dB

B3 gd1 00 = Gain reduction 0 dB

01 = Gain reduction for 5 dB Sets the RX gain reduction, and reduces sensitivity

10 = Gain reduction for 10 dB

B2 gd2 11 = Gain reduction for 15 dB

AGC activation level changed from five times the digitizing level to three

times the digitizing level.

B1 agcr AGC activation level change 1 = 3x

0 = 5x

AGC action can be done any time during receive process. It is not limited

to the start of receive ("max hold").

B0 no-lim AGC action is not limited in time 1 = continuously – no time limit

0 = 8 subcarrier pulses

Table 6-5 shows the various settings for the receiver analog section. It is important to note that setting B4,

B5, B6, and B7 to 0 results to a band-pass characteristic of 240 kHz to 1.4 MHz, which is appropriate for

ISO14443B 106 kbps, ISO14443A/B data-rates of 212 kbps and 424 kbps and FeliCa 424 kbps.

6.5 Receiver – Digital Section

The output of the TRF7970A analog receiver block is a digitized subcarrier signal and is the input to the

digital receiver block. This block includes a Protocol Bit Decoder section and the Framing Logic section.

The protocol bit decoders convert the subcarrier coded signal into a serial bit stream and a data clock.

The decoder logic is designed for maximum error tolerance. This enables the decoder section to

successfully decode even partly corrupted subcarrier signals that otherwise would be lost due to noise or

interference.

In the framing logic section, the serial bit stream data is formatted in bytes. Special signals such as the

start of frame (SOF), end of frame (EOF), start of communication, and end of communication are

automatically removed. The parity bits and CRC bytes are also checked and removed. This "clean" data is

then sent to the

127-byte FIFO register where it can be read by the external microcontroller system. Providing the data this

way, in conjunction with the timing register settings of the TRF7970A means the firmware developer has

to know about much less of the finer details of the ISO protocols to create a very robust application,

especially in low cost platforms where code space is at a premium and high performance is still required.

The start of the receive operation (successfully received SOF) sets the IRQ-flags in the IRQ and Status

(IRQ) to high. When data is received in the FIFO, an interrupt is sent to the MCU to signal that there is

data to be read from the FIFO. The FIFO status register (0x1C) should be used to provide the number of

bytes that should be clocked out during the actual FIFO read.

Any error in the data format, parity, or CRC is detected and notified to the external system by an interrupt-

request pulse. The source condition of the interrupt request pulse is available in the IRQ status register

(0x0C). The main register controlling the digital part of the receiver is the ISO Control register (0x01). By

writing to this register, the user selects the protocol to be used. With each new write in this register, the

default presets are reloaded in all related registers, so no further adjustments in other registers are

needed for proper operation.

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NOTE

If register setting changes are needed for fine tuning the system, they must be done after

setting the ISO Control register (0x01).

The framing section also supports the bit-collision detection as specified in ISO14443A. When a bit

collision is detected, an interrupt request is sent and a flag is set in the IRQ and Status register (0x0C).

The position of the bit collision is written in two registers: Collision Position register (0x0E) and partly in

Collision Position and Interrupt Mask register (0x0D) (bits B6 and B7).

The collision position is presented as sequential bit number, where the count starts immediately after the

start bit. This means a collision in the first bit of a UID would give the value 00 0001 0000 in these

registers when their contents are combined after being read. (the count starts with 0 and the first 16 bits

are the command code and the Number of Valid Bits (NVB) byte).

The receive section also contains two timers. The RX wait time timer is controlled by the value in the RX

Wait Time register (0x08). This timer defines the time interval after the end of the transmit operation in

which the receive decoders are not active (held in reset state). This prevents false detections resulting

from transients following the transmit operation. The value of the RX Wait Time register (0x08) defines the

time in increments of 9.44 µs. This register is preset at every write to ISO Control register (0x01)

according to the minimum tag response time defined by each standard.

The RX no response timer is controlled by the RX No Response Wait Time register (0x07). This timer

measures the time from the start of slot in the anticollision sequence until the start of tag response. If there

is no tag response in the defined time, an interrupt request is sent and a flag is set in the IRQ Status

wait time is stored in the register in increments of 37.76 µs. This register is also preset, automatically for

every new protocol selection.

The digitized output of the analog receiver is at the input of the digital portion of the receiver. This input

signal is the subcarrier coded signal, which is a digital representation of modulation signal on the RF

envelope.

The digital part of the receiver consists of two sections which partly overlap. The first section contains the

bit decoders for the various protocols. The bit decoders convert the subcarrier coded signal to a bit stream

and also the data clock. Thus the subcarrier coded signal is transformed to serial data and the data clock

is extracted. The decoder logic is designed for maximum error tolerance. This enables the decoders to

successfully decode even partly corrupted (due to noise or interference) subcarrier signals.

The second section contains the framing logic for the protocols supported by the bit decoder section. In

the framing section, the serial bit stream data is formatted in bytes. In this process, special signals like the

SOF (start of frame), EOF (end of frame), start of communication, end of communication are automatically

removed. The parity bits and CRC bytes are checked and also removed. The end result is "clean or raw"

data which is sent to the

127-byte FIFO register where it can be read out by the external microcontroller system.

The start of the receive operation (successfully received SOF) sets the flags in the IRQ and Status

request (pin 13 IRQ). If the receive data packet is longer than 96 bytes, an interrupt is sent to the MCU

when the received data occupies 75% of the FIFO capacity to signal that the data should be removed

from the FIFO.

Any error in data format, parity or CRC is detected and the external system is made aware of the error by

an interrupt request pulse. The nature of the interrupt request pulse is available in the IRQ and Status

information in IRQ and Status register differs if the chip is configured as RFID reader or as NFC device

(including tag emulation). The case of NFC operation is presented in Section 6.12.

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The main register controlling the digital part of the receiver is the ISO Control register (address 0x01). By

writing to this register, the user selects the protocol to be used. At the same time (with each new write in

this register) the default preset in all related registers is done, so no further adjustments in other registers

are needed for proper operation. Table 6-6 shows the coding of the ISO Control register (0x01).

Table 6-6. Coding of the ISO Control Register

Bit Signal Name Function Comments

1 = No RX CRC

B7 rx_crc_n Receiving without CRC

0 = RX CRC

0 = output is subcarrier data

B6 dir_mode Direct mode type

1 = output is bit stream and clock from decoder selected by ISO bits

0 = RFID reader mode

B5 rfid RFID mode

1 = NFC or Card Emulator mode

RFID: Mode selection

NFC:

B4 iso_4 RFID protocol, NFC target

0 = NFC target

1 = NFC initiator

RFID: Mode selection (see Table 6-7)

NFC:

B3 iso_3 RFID protocol, NFC mode

0 = passive mode

1 = active mode

RFID: Mode selection

NFC:

B2 iso_2 RFID protocol, Card Emulation

0 = NFC normal modes

1 = Card Emulation mode

RFID: Mode selection

B1 iso_1 RFID protocol, NFC bit rate

NFC: Bit rate selection or Card Emulation selection (see Table 6-8)

RFID: Mode selection

B0 iso_0 RFID protocol, NFC bit rate

NFC: Bit rate selection or Card Emulation selection (see Table 6-8)

Table 6-7. Coding of the ISO Control Register For RFID Mode (B5 = 0)

Iso_4 Iso_3 Iso_2 Iso_1 Iso_0 Protocol Remarks

0 0 0 0 0 ISO15693 low bit rate, one subcarrier, 1 out of 4

0 0 0 0 1 ISO15693 low bit rate, one subcarrier, 1 out of 256

0 0 0 1 0 ISO15693 high bit rate, one subcarrier, 1 out of 4 Default for RFID IC

0 0 0 1 1 ISO15693 high bit rate, one subcarrier, 1 out of 256

0 0 1 0 0 ISO15693 low bit rate, double subcarrier, 1 out of 4

0 0 1 0 1 ISO15693 low bit rate, double subcarrier, 1 out of 256

0 0 1 1 0 ISO15693 high bit rate, double subcarrier, 1 out of 4

0 0 1 1 1 ISO15693 high bit rate, double subcarrier, 1 out of 256

0 1 0 0 0 ISO14443A, bit rate 106 kbps

RX bit rate when TX rate

0 1 0 0 1 ISO14443 A high bit rate 212 kbps different from RX rate (see

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Table 6-7. Coding of the ISO Control Register For RFID Mode (B5 = 0) (continued)

Iso_4 Iso_3 Iso_2 Iso_1 Iso_0 Protocol Remarks

0 1 0 1 0 ISO14443 A high bit rate 424 kbps

0 1 0 1 1 ISO14443 A high bit rate 848 kbps

0 1 1 0 0 ISO14443B, bit rate 106 kbps

RX bit rate when TX rate

0 1 1 0 1 ISO14443 B high bit rate 212 kbps different from RX rate (see

0 1 1 1 0 ISO14443 B high bit rate 424 kbps

0 1 1 1 1 ISO14443 B high bit rate 848 kbps

1 0 0 1 1 Reserved

1 0 1 0 0 Reserved

1 1 0 1 0 FeliCa 212 kbps

1 1 0 1 1 FeliCa 424 kbps

Table 6-8. Coding of the ISO Control Register For NFC

Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1,

B2 = 1)

Card Emulation

Iso_1 Iso_0 NFC (B5 = 1, B2 = 0) (B5 = 1, B2 = 1)

0 0 N/A ISO14443A

0 1 106 kbps ISO14443B

1 0 212 kbps N/A

1 1 424 kbps N/A

6.5.1 Received Signal Strength Indicator (RSSI)

The TRF7970A incorporates in total three independent RSSI building blocks: Internal Main RSSI, Internal

Auxiliary RSSI, and External RSSI. The internal RSSI blocks are measuring the amplitude of the

subcarrier signal; the External RSSI block measures the amplitude of the RF carrier signal at the receiver

input.

6.5.1.1 Internal RSSI – Main and Auxiliary Receivers

Each receiver path has its own RSSI block to measure the envelope of the demodulated RF signal

(subcarrier). Internal Main RSSI and Internal Auxiliary RSSI are identical however connected to different

RF input pins. The Internal RSSI is intended for diagnostic purposes to set the correct RX path conditions.

The Internal RSSI values can be used to adjust the RX gain settings or decide which RX path (Main or

Auxiliary) provides the greater amplitude and hence to decide if the MUX may need to be reprogrammed

to swap the RX input signal. The measuring system latches the peak value, so the RSSI level can be read

after the end of each receive packet. The RSSI register values are reset with every transmission (TX) by

the reader. This ensures an updated RSSI measurement for each new tag response.

The Internal RSSI has 7 steps (3 bit) with a typical increment of approximately 4 dB. The operating range

is between 600 mVPP and 4.2 VPP with a typical step size of approximately 600 mV. Both Internal Main

and Internal Auxiliary RSSI values are stored in the RSSI Levels and Oscillator Status register (0x0F). The

nominal relationship between the input RF peak level and the RSSI value is shown in Figure 6-5.

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0 25 50 75 100 125 150 175 200 225 250 275 300 325

RF Input Voltage Level at RF_IN1 in mVPP

RSSI Levels and Oscillator Status Register value (0x0F)

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25

Input RF Carrier Level in V [V]

RSSI Levels and Oscillator Status Register value (0x0F)

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Figure 6-5. Digital Internal RSSI (Main and Auxiliary) Value vs RF Input Level in VPP (V)

This RSSI measurement is done during the communication to the Tag; this means the TX must be on. Bit

1 in the Chip Status Control register (0x00) defines if Internal RSSI or the External RSSI value is stored in

the RSSI Levels and Oscillator Status register (0x0F). Direct command 0x18 is used to trigger an Internal

RSSI measurement.

6.5.1.2 External RSSI

The External RSSI is mainly used for test and diagnostic to sense the amplitude of any 13.56-MHz signal

at the receivers RX_IN1 input. The External RSSI measurement is typically done in active mode when the

receiver is on but transmitter output is off. The level of the RF signal received at the antenna is measured

and stored in the RSSI Levels and Oscillator Status register 0x0F. The relationship between the voltage at

the RX_IN1 input and the 3-bit code is shown in Figure 6-6.

Figure 6-6. Digital External RSSI Value vs RF Input Level in VPP (mV)

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C1C2

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The relation between the 3-bit code and the external RF field strength (A/m) sensed by the antenna must

be determined by calculation or by experiments for each antenna design. The antenna Q-factor and

connection to the RF input influence the result. Direct command 0x19 is used to trigger an Internal RSSI

measurement.

For clarity, to check the internal or external RSSI value independent of any other operation, the user must:

1. Set transmitter to desired state (on or off) using Bit 5 of Chip Status Control register (0x00) and enable

receiver using Bit 1.

2. Check internal or external RSSI using direct commands 0x18 or 0x19, respectively. This action places

the RSSI value in the RSSI register.

3. Delay at least 50 µs.

4. Read the RSSI register using direct command 0x0F; values range from 0x40 to 0x7F.

5. Repeat steps 1-4 as desired, as register is reset after it is read.

6.6 Oscillator Section

The 13.56-MHz or 27.12-MHz crystal (or oscillator) is controlled by the Chip Status Control register (0x00)

and the EN and EN2 terminals. The oscillator generates the RF frequency for the RF output stage as well

as the clock source for the digital section. The buffered clock signal is available at pin 27 (SYS_CLK) for

any other external circuits. B4 and B5 inside the Modulation and SYS_CLK register (0x09) can be used to

divide the external SYS_CLK signal at pin 27 by 1, 2 or 4.

Typical start-up time from complete power down is in the range of 3.5 ms.

During Power Down Mode 2 (EN = 0, EN2 = 1) the frequency of SYS_CLK is switched to 60 kHz (typical).

The crystal needs to be connected between pin 30 and pin 31. The external shunt capacitors values for C1

and C2must be calculated based on the specified load capacitance of the crystal being used. The external

shunt capacitors are calculated as two identical capacitors in series plus the stray capacitance of the

TRF7970A and parasitic PCB capacitance in parallel to the crystal.

The parasitic capacitance (CS, stray and parasitic PCB capacitance) can be estimated at 4 to 5 pF

(typical).

As an example, using a crystal with a required load capacitance (CL) of 18 pF, the calculation is shown in

Equation 1.

C1= C2= 2 × (CL– CS) = 2 × (18 pF – 4.5 pF) = 27 pF (1)

A 27-pF capacitor must be placed on pins 30 and 31 to ensure proper crystal oscillator operation.

Figure 6-7. Crystal Block Diagram

Any crystal used with TRF7970A should have minimum characteristics shown in Table 6-9.

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Table 6-9. Minimum Crystal Requirements

Parameter Specification

Frequency 13.56 MHz or 27.12 MHz

Mode of Operation Fundamental

Type of Resonance Parallel

Frequency Tolerance ±20 ppm

Aging < 5 ppm/year

Operation Temperature Range -40°C to 85°C

Equivalent Series Resistance 50 Ω

As an alternative, an external clock oscillator source can be connected to Pin 31 to provide the system

clock; pin 30 can be left open.

6.7 Transmitter – Analog Section

The 13.56-MHz oscillator generates the RF signal for the PA stage. The power amplifier consists of a

driver with selectable output resistance of nominal 4 Ωor 8 Ω. The transmit power level is set by bit B4 in

the Chip Status Control register (0x00). The transmit power levels are selectable between 100 mW (half

power) or 200 mW (full power) when configured for 5-V automatic operation. The transmit power levels

are selectable between 33 mW (half power) or 70 mW (full power) when configured for 3-V automatic

operation.

The ASK modulation depth is controlled by bits B0, B1, and B2 in the Modulator and SYS_CLK Control

External control of the transmit modulation depth is possible by setting the ISO Control register (0x01) to

direct mode. While operating the TRF7970A in direct mode, the transmit modulation is made possible by

selecting the modulation type ASK or OOK at pin 12. External control of the modulation type is made

possible only if enabled by setting B6 in the Modulator and SYS_CLK Control register (0x09) to 1.

In normal operation mode, the length of the modulation pulse is defined by the protocol selected in the

ISO Control register (0x01). With a high-Q antenna, the modulation pulse is typically prolonged, and the

tag detects a longer pulse than intended. For such cases, the modulation pulse length needs to be

corrected by using the TX Pulse Length Control register (0x06).

If the register contains all zeros, then the pulse length is governed by the protocol selection. If the register

contains a value other than 0x00, the pulse length is equal to the value of the register multiplied by

73.7 ns; therefore, the pulse length can be adjusted between 73.7 ns and 18.8 µs in 73.7-ns increments.

6.8 Transmitter – Digital Section

The digital part of the transmitter is a mirror of the receiver. The settings controlled the ISO Control

TRF7970A automatically adds these special signals: start of communication, end of communication, SOF,

EOF, parity bits, and CRC bytes.

The data is then coded to modulation pulse levels and sent to the RF output stage modulation control unit.

Similar to working with the receiver, this means that the external system MCU only has to load the FIFO

with data and all the microcoding is done automatically, again saving the firmware developer code space

and time. Additionally, all of the registers used for transmit parameter control are automatically preset to

optimum values when a new selection is entered into the ISO Control register (0x01).

Note: FIFO must be reset before starting any transmission with Direct Command 0x0F.

There are two ways to start the transmit operation:

• Load the number of bytes to be sent into registers 0x1D and 0x1E and load the data to be sent into the

FIFO (address 0x1F), followed by sending a transmit command (see Direct Commands section). The

transmission then starts when the transmit command is received.

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• Send the transmit command and the number of bytes to be transmitted first, and then start to send the

data to the FIFO. The transmission starts when first data byte is written into the FIFO.

NOTE

If the data length is longer than the FIFO, the TRF7970A notifies the external system MCU

when most of the data from the FIFO has been transmitted by sending an interrupt request

with a flag in the IRQ register to indicate a FIFO low or high status. The external system

should respond by loading the next data packet into the FIFO.

At the end of a transmit operation, the external system MCU is notified by interrupt request (IRQ) with a

flag in IRQ register (0x0C) indicating TX is complete (example value = 0x80).

The TX Length registers also support incomplete byte transmission. The high two nibbles in register 0x1D

and the nibble composed of bits B4 through B7 in register 0x1E store the number of complete bytes to be

transmitted. Bit B0 in register 0x1E is a flag indicating that there are also additional bits to be transmitted

that do not form a complete byte. The number of bits is stored in bits B1 through B3 of the same register

(0x1E).

Some protocols have options, and there are two sublevel configuration registers to select the TX protocol

options.

• ISO14443B TX Options register (0x02). This register controls the SOF and EOF selection and EGT

selection for the ISO14443B protocol.

• ISO14443A High Bit Rate Options and Parity register (0x03). This register enables the use of different

bit rates for RX and TX operations in the ISO14443 high bit rate protocol and also selects the parity

method in the ISO14443A high bit rate protocol.

The digital section also has a timer. The timer can be used to start the transmit operation at a specified

time in accordance with a selected event.

6.9 Transmitter – External Power Amplifier and Subcarrier Detector

The TRF7970A can be used in conjunction with an external TX power amplifier or external subcarrier

detector for the receiver path. In this case, certain registers must be programmed as shown here:

• Bit B6 of the Regulator and I/O Control register (0x0B) must be set to 1. This setting has two functions:

first, to provide a modulated signal for the transmitter if needed, and second, to configure the

TRF7970A receiver inputs for an external demodulated subcarrier input.

• Bit B3 of the Modulation and SYS_CLK Control register (0x09) must be set to 1 (see

Section 6.14.3.2.8). This function configures the ASK/OOK pin for either a digital or analog output (B3

= 0 enables a digital output, B3 = 1 enables an analog output). The design of an external power

amplifier requires detailed RF knowledge. There are also readily designed and certified high-power HF

reader modules on the market.

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6.10 TRF7970A IC Communication Interface

6.10.1 General Introduction

The communication interface to the reader can be configured in two ways: with a eight line parallel

interface (D0:D7) plus DATA_CLK, or with a three or four wire Serial Peripheral Interface (SPI). The SPI

interface uses traditional Master Out/Slave In (MOSI), Master In/Slave Out (MISO), IRQ, and DATA_CLK

lines. The SPI can be operated with or without using the Slave Select line.

These communication modes are mutually exclusive; that is, only one mode can be used at a time in the

application.

When the SPI interface is selected, the unused I/O_2, I/O_1, and I/O_0 pins must be hard-wired as shown

in Table 6-10. At power up, the TRF7970A samples the status of these three pins and then enters one of

the possible SPI modes.

The TRF7970A always behaves as the slave device, and the microcontroller (MCU) behaves as the

master device. The MCU initiates all communications with the TRF7970A, and the TRF7970A makes use

of the Interrupt Request (IRQ) pin in both parallel and SPI modes to prompt the MCU for servicing

attention.

Table 6-10. Pin Assignment in Parallel and Serial Interface Connection or Direct Mode

Pin Parallel Parallel (Direct Mode) SPI With SS SPI Without SS(1)

DATA_ CLK DATA_CLK DATA_CLK DATA_CLK from master DATA_CLK from master

I/O_7 A/D[7] (not used) MOSI(2) = data in (reader in) MOSI(2) = data in (reader in)

Direct mode, data out (subcarrier

I/O_6 A/D[6] MISO(3) = data out (MCU out) MISO(3) = data out (MCU out)

or bit stream)

Direct mode, strobe – bit clock

I/O_5(4) A/D[5] See (4) See (4)

out

I/O_4 A/D[4] (not used) SS – slave select(5) (not used)

I/O_3 A/D[3] (not used) (not used) (not used)

I/O_2 A/D[2] (not used) At VDD At VDD

I/O_1 A/D[1] (not used) At VDD At VSS

I/O_0 A/D[0] (not used) At VSS At VSS

IRQ IRQ interrupt IRQ interrupt IRQ interrupt IRQ interrupt

(1) FIFO is not accessible in SPI without SS mode. See device errata for detailed information.

(2) MOSI = Master Out, Slave In

(3) MISO = Master In, Slave Out

(4) I/O_5 pin is used only for information when data is put out of the chip (for example, reading 1 byte from the chip). It is necessary first to

write in the address of the register (8 clocks) and then to generate another 8 clocks for reading out the data. The I/O_5 pin goes high

during the second 8 clocks. But for normal SPI operations, I/O_5 pin is not used.

(5) Slave_Select pin is active low

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Communication is initialized by a start condition, which is expected to be followed by an

Address/Command word (Adr/Cmd). The Adr/Cmd word is 8 bits long, and Table 6-11 shows its format.

Table 6-11. Address and Command Word Bit Distribution

Bit Description Bit Function Address Command

0 = address

B7 Command control bit 0 1

1 = command

0 = write

B6 Read/Write R/W 0

1 = read

B5 Continuous address mode 1 = Continuous mode R/W 0

B4 Address/Command bit 4 Adr 4 Cmd 4

B3 Address/Command bit 3 Adr 3 Cmd 3

B2 Address/Command bit 2 Adr 2 Cmd 2

B1 Address/Command bit 1 Adr 1 Cmd 1

B0 Address/Command bit 0 Adr 0 Cmd 0

The MSB (bit 7) determines if the word is to be used as a command or as an address. The last two

columns of Table 6-11 show the function of the separate bits if either address or command is written. Data

is expected once the address word is sent. In continuous-address mode (Cont. mode = 1), the first data

that follows the address is written (or read) to (from) the given address. For each additional data, the

address is incremented by one. Continuous mode can be used to write to a block of control registers in a

single stream without changing the address; for example, setup of the predefined standard control

registers from the MCU non-volatile memory to the reader. In non-continuous address mode (simple

addressed mode), only one data word is expected after the address.

Address Mode is used to write or read the configuration registers or the FIFO. When writing more than 12

bytes to the FIFO, the Continuous Address Mode should be set to 1.

The Command Mode is used to enter a command resulting in reader action (for example, initialize

transmission, enable reader, and turn reader on or off).

Examples of expected communications between an MCU and the TRF7970A are shown in the following

sections.

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6.10.1.1 Continuous Address Mode

Table 6-12. Continuous Address Mode

Start Adr x Data(x) Data(x+1) Data(x+2) Data(x+3) Data(x+4) ... Data(x+n) StopCont

Figure 6-8. Continuous Address Register Write Example Starting with Register 0x00 Using SPI With SS

Figure 6-9. Continuous Address Register Read Example Starting with Register 0x00 Using SPI With SS

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6.10.1.2 Noncontinuous Address Mode (Single Address Mode)

Table 6-13. Noncontinuous Address Mode (Single Address Mode)

Start Adr x Data(x) Adr y Data(y) ... Adr z Data(z) StopSgl

Figure 6-10. Single Address Register Write Example of Register 0x00 Using SPI With SS

Figure 6-11. Single Address Register Read Example of Register 0x00 Using SPI With SS

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6.10.1.3 Direct Command Mode

Table 6-14. Direct Command Mode

Start Cmd x (Optional data or command) Stop

Figure 6-12. Direct Command Example of Sending 0x0F (Reset) Using SPI With SS

The other Direct Command Codes from MCU to TRF7970A IC are described in Section 6.13.

6.10.1.4 FIFO Operation

The FIFO is a 127-byte register at address 0x1F with byte storage locations 0 to 126. FIFO data is loaded

in a cyclical manner and can be cleared by a reset command (0x0F) (see Figure 6-12 showing this Direct

Command).

Associated with the FIFO are two counters and three FIFO status flags. The first counter is a 7-bit FIFO

byte counter (bits B0 to B6 in register 0x1C) that tracks the number of bytes loaded into the FIFO. If the

number of bytes in the FIFO is n, the register value is n (number of bytes in FIFO register). For example, if

8 bytes are in the FIFO, the FIFO counter (Register 0x1C) has the hexadecimal value of 0x08 (binary

value of 00001000).

A second counter (12 bits wide) indicates the number of bytes being transmitted (registers 0x1D and

0x1E) in a data frame. An extension to the transmission-byte counter is a 4-bit broken-byte counter also

provided in register 0x1E (bits B0 to B3). Together these counters make up the TX length value that

determines when the reader generates the EOF byte.

FIFO status flags are as follows:

•FIFO overflow (bit B7 of register 0x1C) – indicates that the FIFO has more than 127 bytes loaded

During transmission, the FIFO is checked for an almost-empty condition, and during reception for an

almost-full condition. The maximum number of bytes that can be loaded into the FIFO in a single

sequence is 127 bytes.

NOTE

The number of bytes in a frame, transmitted or received, can be greater than 127 bytes.

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During transmission, the MCU loads the TRF7970A IC's FIFO (or during reception the MCU removes data

from the FIFO), and the FIFO counter counts the number of bytes being loaded into the FIFO. Meanwhile,

the byte counter keeps track of the number of bytes being transmitted. An interrupt request is generated if

the number of bytes in the FIFO is less than 32 or greater than 96, so that MCU can send new data or

remove the data as necessary. The MCU also checks the number of data bytes to be sent, so as to not

surpass the value defined in TX length bytes. The MCU also signals the transmit logic when the last byte

of data is sent or was removed from the FIFO during reception. Transmission starts automatically after the

first byte is written into FIFO.

Figure 6-13. Example of Checking the FIFO Status Register Using SPI With SS

6.10.2 Parallel Interface Mode

In parallel mode, the start condition is generated on the rising edge of the I/O_7 pin while the CLK is high.

This is used to reset the interface logic. Figure 6-14 shows the sequence of the data, with an 8-bit address

word first, followed by data.

Communication is ended by:

• The StopSmpl condition, where a falling edge on the I/O_7 pin is expected while CLK is high.

• The StopCont condition, where the I/O_7 pin must have a successive rising and falling edge while CLK

is low to reset the parallel interface and be ready for the new communication sequence.

• The StopSmpl condition is also used to terminate the direct mode.

Figure 6-14. Parallel Interface Communication With Simple Stop Condition (StopSmpl)

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Figure 6-15. Parallel Interface Communication with Continuous Stop Condition (StopCont)

Figure 6-16. Example of Parallel Interface Communication With Continuous Stop Condition

6.10.3 Reception of Air Interface Data

At the start of a receive operation (when SOF is successfully detected), B6 is set in the IRQ Status

receive data string is shorter than or equal to the number of bytes configured in the Adjustable FIFO IRQ

Levels register (0x14). An IRQ_FIFO interrupt request is sent to the MCU during the receive operation if

the data string is greater than the level set in the Adjustable FIFO IRQ Levels register (0x14). After

receiving an IRQ_FIFO or RX complete interrupt, the MCU must read the FIFO status register (0x1C) to

determine the number of bytes to be read from the FIFO. Next, the MCU must read the data in the FIFO.

It is optional to read the FIFO status register (0x1C) after reading FIFO data to determine if the receive is

complete. In the case of an IRQ_FIFO, the MCU should expect either another IRQ_FIFO or RX complete

interrupt. This is repeated until an RX complete interrupt is generated. The MCU receives the interrupt

request, then checks to determine the reason for the interrupt by reading the IRQ Status register (0x0C),

after which the MCU reads the data from the FIFO.

If the reader detects a receive error, the corresponding error flag is set (framing error, CRC error) in the

IRQ Status register, indicating to the MCU that reception was not completed correctly.

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6.10.4 Data Transmission to MCU

Before beginning data transmission, the FIFO should always be cleared with a reset command (0x0F).

Data transmission is initiated with a selected command (see Section 6.13). The MCU then commands the

reader to do a continuous write command (0x3D) starting from register 0x1D. Data written into register

0x1D is the TX Length Byte 1 (upper and middle nibbles), while the following byte in register 0x1E is the

TX Length Byte 2 (lower nibble and broken byte length) (see Table 6-57 and Table 6-58) . Note that the

TX byte length determines when the reader sends the end of frame (EOF) byte. After the TX length bytes

are written, FIFO data is loaded in register 0x1F with byte storage locations 0 to 127. Data transmission

begins automatically after the first byte is written into the FIFO. The loading of TX length bytes and the

FIFO can be done with a continuous-write command, as the addresses are sequential.

At the start of transmission, the flag B7 (IRQ_TX) is set in the IRQ Status register, and at the end of the

transmit operation, an interrupt is sent to inform the MCU that the task is complete.

6.10.5 Serial Interface Communication (SPI)

When an SPI interface is used, I/O pins I/O_2, I/O_1, and I/O_0 must be hard wired according to Table 6-

10. On power up, the TRF7970A looks for the status of these pins and then enters into the corresponding

mode.

The choice of one of these modes over another should be predicated by the available GPIOs and the

desired control of the system.

The serial communications work in the same manner as the parallel communications with respect to the

FIFO, except for the following condition. On receiving an IRQ from the reader, the MCU reads the

TRF7970A IRQ Status register to determine how to service the reader. After this, the MCU must to do a

dummy read to clear the reader's IRQ status register. The dummy read is required in SPI mode because

the reader's IRQ status register needs an additional clock cycle to clear the register. This is not required in

parallel mode because the additional clock cycle is included in the Stop condition. When first establishing

communications with the TRF7970A, the SOFT_INIT (0x03) and IDLE (0x00) commands should be sent

first from the MCU (see Table 6-19).

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Read Data

IRQ Status

Dummy Read

Write

Address

Byte

(0x6C)

No Data Transitions (All High or Low)

Don’t Care Ignore

B7 B6 B5 B4 B3 B2 B1 B0

SLAVE

SELECT

MISO

MOSI

DATA _CLK

No Data Transitions (All High or Low)

B7 B6 B5 B4 B3 B2 B1 B0

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The procedure for a dummy read is as follows:

1. Start the dummy read:

(a) When using slave select (SS): set SS bit low.

(b) When not using SS: start condition is when Data Clock is high (see Table 6-10).

2. Send address word to IRQ status register (0x0C) with read and continuous address mode bits set to 1

(see Table 6-10).

3. Read 1 byte (8 bits) from IRQ status register (0x0C).

4. Dummy-read 1 byte from register 0x0D (collision position and interrupt mask).

5. Stop the dummy read:

(a) When using slave select (SS): set SS bit high.

(b) When not using SS: stop condition when Data Clock is high.

Figure 6-17. Procedure for Dummy Read

Figure 6-18. Example of Dummy Read Using SPI With SS

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SLAVE

SELECT

MISO

MOSI

DATA

CLK

WRITE

ADDRESS BYTE

READ DATA

BYTE 1

READ DATA

BYTE n

DON’T CARE

No Data Transitions (All High or Low) No Data Transitions (All High or Low)

B7 B6 B5 B4 B3 B2 B1 B0

B7 B6 B5 B4 B3 B2 B1 B0 B7 B6 B5 B4 B3 B2 B1 B0

b0MISO

MOSI

DATA

CLK

WRITE

MOSI Transitions on Data Clock

Rising Edge

MOSI Valid on Data Clock Falling Edge

tSTE,LEAD

tLO/HI tLO/HI

b6…b1 b0

tSU,SI tHD,SI

1/fUCxCLK tSTE,DIS

b6...b1

tVALID,SO

tSTE,LAG

tHD,SO

DON’T CARE

READ

Data Transition is on Data Clock

Rising Edge

MISO Valid on Data Clock Falling Edge

tSU,SO

NO DATA TRANSITIONS

(ALL HIGH/LOW)

Slave

Select

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6.10.5.1 Serial Interface Mode With Slave Select (SS)

The serial interface is in reset while the Slave Select signal is high. Serial data in (MOSI) changes on the

rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19. Communication is

terminated when the Slave Select signal goes high.

All words must be 8 bits long with the MSB transmitted first.

Figure 6-19. SPI With Slave Select Timing Diagram

The read command is sent out on the MOSI pin, MSB first, in the first eight clock cycles. MOSI data

changes on the rising edge, and is validated in the reader on the falling edge, as shown in Figure 6-19.

During the write cycle, the serial data out (MISO) is not valid. After the last read command bit (B0) is

validated at the eighth falling edge of SCLK, valid data can be read on the MISO pin at the falling edge of

SCLK. It takes eight clock edges to read out the full byte (MSB first). See Section 5.3 for electrical

specifications related to Figure 6-19.

The continuous read operation is shown in Figure 6-20.

Figure 6-20. Continuous Read Operation Using SPI With Slave Select

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Figure 6-21. Continuous Read of Registers 0x00 Through 0x05 Using SPI With SS

Performing Single Slot Inventory Command as an example is shown in Figure 6-22. Reader registers (in

this example) are configured for 5 VDC in and default operation.

Figure 6-22. Inventory Command Sent From MCU to TRF7970A

The TRF7970A takes these bytes from the MCU and then send out Request Flags, Inventory Command

,and Mask over the air to the ISO15693 transponder. After these three bytes have been transmitted, an

interrupt occurs to indicate back to the reader that the transmission has been completed. In the example in

Figure 6-23, this IRQ occurs approximately 1.6 ms after the SS line goes high after the Inventory

command is sent out.

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Figure 6-23. IRQ After Inventory Command

The IRQ status register read (0x6C) yields 0x80, which indicates that TX is indeed complete. This is

followed by a dummy clock. Then, if a tag is in the field and no error is detected by the reader, a second

interrupt is expected and occurs (in this example) approximately 4 ms after first IRQ is read and cleared.

In the continuation of the example (see Figure 6-24), the IRQ Status Register is read using method

previously recommended, followed by a single read of the FIFO status register, which indicates that there

are 10 bytes to be read out.

Figure 6-24. Read IRQ Status Register After Inventory Command

This is then followed by a continuous read of the FIFO. The first byte is (and should be) 0x00 for no error.

The next byte is the DSFID (usually shipped by manufacturer as 0x00), then the UID, shown here up to

the next most significant byte, the MFG code (shown as 0x07 (TI silicon)).

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Figure 6-25. Continuous Read of FIFO After Inventory Command

At this point, it is good form to reset the FIFO and then read out the RSSI value of the tag. In this case the

transponder is very close to the antenna, so value of 0x7F is recovered.

Figure 6-26. Reset FIFO and Read RSSI

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Analog Front End (AFE)

14443A

ISO Encoders/Decoders

14443B 15693 FeliCa

Packetization/Framing

Microcontroller

Direct Mode 0:

Raw RF Sub-Carrier

Data Stream

Direct Mode 1:

Raw Digital ISO Coded

Data Without

Protocol Frame

ISO Mode:

Full ISO Framing

and Error Checking

(Typical Mode)

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6.10.6 Direct Mode

Direct mode allows the user to configure the reader in one of two ways. Direct Mode 0 (bit 6 = 0, as

defined in ISO Control register) allows the user to use only the front-end functions of the reader,

bypassing the protocol implementation in the reader. For transmit functions, the user has direct access to

the transmit modulator through the MOD pin (pin 14). On the receive side, the user has direct access to

the subcarrier signal (digitized RF envelope signal) on I/O_6 (pin 23).

Direct Mode 1 (bit 6 = 1, as defined in ISO Control register) uses the subcarrier signal decoder of the

selected protocol (as defined in ISO Control register). This means that the receive output is not the

subcarrier signal but the decoded serial bit stream and bit clock signals. The serial data is available on

I/O_6 (pin 23) and the bit clock is available on I/O_5 (pin 22). The transmit side is identical; the user has

direct control over the RF modulation through the MOD input. This mode is provided so that the user can

implement a protocol that has the same bit coding as one of the protocols implemented in the reader, but

needs a different framing format.

To select direct mode, the user must first choose which direct mode to enter by writing B6 in the ISO

Control register. This bit determines if the receive output is the direct subcarrier signal (B6 = 0) or the

serial data of the selected decoder. If B6 = 1, then the user must also define which protocol should be

used for bit decoding by writing the appropriate setting in the ISO Control register.

The reader actually enters the direct mode when B6 (direct) is set to 1 in the chip status control register.

Direct mode starts immediately. The write command should not be terminated with a stop condition (see

communication protocol), because the stop condition terminates the direct mode and clears B6. This is

necessary as the direct mode uses one or two I/O pins (I/O_6, I/O_5). Normal parallel communication is

not possible in direct mode. Sending a stop condition terminates direct mode.

Figure 6-27 shows the different configurations available in direct mode.

• In mode 0, the reader is used as an AFE only, and protocol handling is bypassed.

• In mode 1, framing is not done, but SOF and EOF are present. This allows for a user-selectable

framing level based on an existing ISO standard.

• In mode 2, data is ISO-standard formatted. SOF, EOF, and error checking are removed, so the

microprocessor receives only bytes of raw data through a 127-byte FIFO.

Figure 6-27. User-Configurable Modes

The steps to enter Direct Mode are listed below, using SPI with SS communication method only as one

example, as Direct Modes are also possible with parallel and SPI without SS. The must enter Direct Mode

0 to accommodate non-ISO standard compliant card type communications. Direct Mode can be entered at

any time, so in the event a card type started with ISO standard communications, then deviated from the

standard after being identified and selected, the ability to go into Direct Mode 0 becomes very useful.

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Step 1: Configure Pins I/O_0 to I/O_2 for SPI with SS

Step 2: Set Pin 12 of the TRF7970A (ASK/OOK pin) to 0 for ASK or 1 for OOK

Step 3: Program the TRF7970A registers

The following registers need to be explicitly set before going into the Direct Mode.

1. ISO Control register (0x01) to the appropriate standard

– 0x02 for ISO 15693 High Data Rate

– 0x08 for ISO14443A (106 kbps)

– 0x1A for FeliCa 212 kbps

– 0x1B for FeliCa 424 kbps

2. Modulator and SYS_CLK register (0x09) to the appropriate clock speed and modulation

– 0x21 for 6.78 MHz Clock and OOK (100%) modulation

– 0x20 for 6.78 MHz Clock and ASK 10% modulation

– 0x22 for 6.78 MHz Clock and ASK 7% modulation

– 0x23 for 6.78 MHz Clock and ASK 8.5% modulation

– 0x24 for 6.78 MHz Clock and ASK 13% modulation

– 0x25 for 6.78 MHz Clock and ASK 16% modulation

(See register 0x09 definition for all other possible values)

Example register setting for ISO14443A at 106 kbps:

• ISO Control register (0x01) to 0x08

• RX No Response Wait Time register (0x07) to 0x0E

• RX Wait Time register (0x08) to 0x07

• Modulator control register (0x09) to 0x21 (or any custom modulation)

• RX Special Settings register (0x0A) to 0x20

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Step 4: Entering Direct Mode 0

The following registers need to be programmed to enter Direct Mode 0

1. Set bit B6 of the Modulator and SYS_CLK Control register (0x09) to 1.

2. Set bit B6 of the ISO Control (Register 01) to 0 for Direct Mode 0 (default its 0)

3. Set bit B6 of the Chip Status Control register (0x00) to 1 to enter Direct Mode

4. Send extra eight clock cycles (see Figure 6-28, this step is TRF7970A specific)

NOTE

– It is important that the last write is not terminated with a stop condition. For SPI, this

means that Slave Select (I/O_4) stays low.

– Sending a Stop condition terminates the Direct Mode and clears bit B6 in the Chip Status

Control register (0x00).

NOTE

Access to Registers, FIFO, and IRQ is not available during Direct Mode 0.

The reader enters the Direct Mode 0 when bit 6 of the Chip Status Control register (0x00) is set to a 1 and

stays in Direct Mode 0 until a stop condition is sent from the microcontroller.

NOTE

The write command should not be terminated with a stop condition (for example, in SPI

mode this is done by bringing the Slave Select line high after the register write), because the

stop condition terminates the direct mode and clears bit 6 of the Chip Status Control register

(0x00), making it a 0.

Figure 6-28. Entering Direct Mode 0

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TRF7970A Microcontroller

Drive the MOD pin

according to the data coding

specified by the standard

Decode the subcarrier

information according

to the standard

MOD

(Pin 14)

I/O_6

(Pin 23)

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Step 5: Transmit Data Using Direct Mode

The application now has direct control over the RF modulation through the MOD input (see Figure 6-29).

Figure 6-29. Direct Control Signals

The microcontroller is responsible for generating data according to the coding specified by the particular

standard. The microcontroller must generate SOF, EOF, Data, and CRC. In direct mode, the FIFO is not

used and no IRQs are generated. See the applicable ISO standard to understand bit and frame

definitions. As an example of what the developer sees when using DM0 in an actual application, Figure 6-

30 is presented to clearly show the relationship between the MOD pin being controlled by the MCU and

the resulting modulated 13.56-MHz carrier signal.

Figure 6-30. TX Sequence Out in DM0

Step 6: Receive Data Using Direct Mode

After the TX operation is complete, the tag responds to the request and the subcarrier data is available on

pin I/O_6. The microcontroller needs to decode the subcarrier signal according to the standard. This

includes decoding the SOF, data bits, CRC, and EOF. The CRC then needs to be checked to verify data

integrity. The receive data bytes must be buffered locally.

As an example of the receive data bits and framing level according to the ISO14443A standard is shown

in Figure 6-31 (taken from ISO14443 specification and TRF7970A air interface).

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128/fc = 9.435 µs = t (106-kbps data rate)

64/fc = 4.719 µs = t time

32/fc = 2.359 µs = t time

t = 9.44

bµs t = 4.72

xµs t = 2.48

1µs

Sequence Y = Carrier for 9.44 µs Sequence Z = Pause for 2

Carrier for Remainder of 9.44

to 3 µs,

µs

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Figure 6-31. Receive Data Bits and Framing Level

Figure 6-32 is presented to clearly show an example of what the developer should expect on the I/O_6

line during the RX process while in Direct Mode 0.

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Figure 6-32. RX Sequence on I/O_6 in DM0 (Analog Capture)

Step 7: Terminating Direct Mode 0

After the EOF is received, data transmission is over, and Direct Mode 0 can be terminated by sending a

Stop Condition (in the case of SPI, make the Slave Select go high). The TRF7970A is returned to default

state.

6.11 Special Direct Mode for Improved MIFARE™ Compatibility

See the application report TRF7970A Firmware Design Hints (SLOA159).

6.12 NFC Modes

6.12.1 Target

When used as the NFC target, the chip is typically in a power down or standby mode. If EN2 = H, the chip

keeps the supply system on. If EN2 = L and EN = L the chip is in complete power down. To operate as

NFC target or Tag emulator, the MCU must load a value different from zero (0) in Target Detection Level

during complete power down and consumes only 3.5 µA). The RF measurement constantly monitors the

RF signal on the antenna input. When the RF level on the antenna input exceeds the level defined in the

in Target Detection Level register, the chip is automatically activated (EN is internal forced high). The

typical RF value that causes power-up for each value of B0 to B2 and the function of Target Detection

Level register is listed in Table 6-15.

NFC Target Detection Level Register (0x18) – defines level for RF level for wake-up and gives

information of NFCID size. This register is directly supplied by VEXT to ensure data retention during

complete power down.

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Table 6-15. NFC Target Detection Level Register

Bit Signal Name Function Comments

B7 Id_s1 NFCID1 size used in 106 kbps passive target SDD

B6 Id_s0

Automatic SDD using internal state machine and ID

B5 Sdd_en 1 = Enables internal SDD protocol stored in NFCID Number register(1)

B4 N/A

B3 Hi_rf Extended range for RF measurements

B2 Rfdet_h2 RF field level required for system wake-up. If all Comparator output is displayed in NFC Target

B1 Rfdet_h1 bits are 0, the RF level detection is switched off. Protocol register B7 (rf_h)

B0 Rfdet_h0

(1) Refer to the device errata (SLOZ011) for details on automatic SDD dependencies.

Default: reset to 00 at POR on VEXT (not on POR based on VDD_X), not reset at EN = 0

Table 6-16. Bits B0 to B3 of the NFC Target Detection Level Register

b0 B1 B2 000 001 010 011 100 101 110 111

B3 = 0 RF Vpp Not active 480 mV 350 mV 250 mV 220 mV 190 mV 180 mV 170 mV

B3 = 1 RF Vpp Not active 1500 mV 700 mV 500 mV 450 mV 400 mV 320 mV 280 mV

When the voltage supply system and the oscillator are started and is stable, the osc_ok goes high (B6 of

RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).

Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly

also during normal operation). This informs the MCU that the chip should start operation as an NFC

TARGET device.

When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set in IRQ

internal power-up ends after the second IRQ. The type and coding of the first initiator (or reader in the

case of a tag emulator) command define the communication protocol type which the target must use. So

the communication protocol type is available in the NFC Target Protocol register immediately after

receiving the first command. The coding of the NFC Target Protocol register is described next.

NFC Target Protocol Register (0x19) – displays the bit rate and protocol type (active or passive)

transmitted by initiator in the first command. It also displays the comparator outputs of both RF level

detectors.

Table 6-17. NFC Target Protocol Register

Bit Signal Name Function Comments

The wake-up level is defined by bits b0-b3 of NFC

B7 Rf_h 1 = RF level is above the set wake-up level Target Detection Level register

1 = RF level is above the RF collision avoidance The collision avoidance level is defined by bits b0-

B6 Rf_l level. b2 of NFC Low Field Detection Level register

B5 N/A

1 = FeliCa type The first initiator command had physical level

B4 FeliCa 0 = ISO14443A type coding like FeliCa or like ISO14443A

The first initiator/reader command was SENS_REQ

B3 Pas106 Passive target 106 kbps or tag emulation or ALL_REQ

B2 Pas14443B Tag emulation ISO14443B The first reader command was of ISO14443B type

B1 Nfcbr1 00 = N/A

01 = 106 kbps

Bit rate of first received command 10 = 212 kbps

B0 Nfcbr0 11 = 424 kbps

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Default: reset to 00 at POR and EN = L. B0 to B4 are automatically reset after MCU read operation. B6

and B7 continuously display the RF level comparator outputs.

Based on the first command from INITIATOR following actions are taken:

• If the first command is SENS_REQ or ALL_REQ, the TARGET must enter the SDD protocol for 106

kbps passive communication. If bit B5 in NFC Target Detection Level register is not set, the MCU

handles the SDD and the command received is send to FIFO. If the RF field is turned off (B7 in the

NFC Target Protocol register goes low) at any time, the system sends an IRQ to the MCU with bit B2

(RF field change) in the IRQ register set high. This informs the MCU that the procedure was aborted

and the system must be reset. The clock extractor is automatically activated in this mode.

• If the command is SENS_REQ or ALL_REQ and the Tag emulation bit in ISO Control register is set,

the system emulates an ISO14443A tag. The procedure does not differ from the one previously

described for a passive target at 106 kbps. The clock extractor is automatically activated in this mode.

• If the first command is a POLLING request, the system becomes a TARGET in passive communication

using 212 kbps or 424 kbps. The SDD is relatively simple and is handled by the MCU directly. The

POLLING response is sent in one of the slots automatically calculated by the MCU (first slot starts

2.416 ms after the end of the command and slots follow in 1.208 ms).

• If the first command is ATR_REQ, the system operates as an active TARGET using the same

communication speed and bit coding as used by the INITIATOR. Again, all of the replies are handled

by MCU. The chip is only required to time the response collision avoidance, which is done on direct

command from MCU. When the RF field is switched on and the minimum wait time is elapsed, the chip

sends an IRQ with B1 (RF collision avoidance finished) set high. This signals the MCU that it can send

the reply.

• If the first command is coded as ISO14443B and the Tag emulation bit is set in the ISO Control

and the chip provides all physical level coding, decoding, and framing for this protocol.

Table 6-18 shows the function of the IRQ and Status register in NFC and Tag emulation. This register is

preset to 0 at POR = H or EN = L and at each write to ISO Control. It is also automatically reset at the end

of read phase. The reset also removes the IRQ flag.

Table 6-18. IRQ and Status Register (0x0C) for NFC and Card Emulation Operation (1)

Bit Name Function Description

Signals that TX is in progress. The flag is set at the start of

B7 Irq_tx IRQ set due to end of TX TX but the interrupt request (IRQ = 1) is sent when TX is

finished.

Signals that RX SOF was received and RX is in progress.

B6 Irg_srx IRQ set due to RX start The flag is set at the start of RX but the interrupt request

(IRQ = 1) is sent when RX is finished.

Signals FIFO high or low as set in the Adjustable FIFO IRQ

B5 Irq_fifo Signals the FIFO level Levels (0x14) register

Indicates receive CRC error only if B7 (no RX CRC) of ISO

B4 Irq_err1 CRC error Control register is set to 0.

B3 Irq_err2 Parity error Indicates parity error for ISO14443A

B2 Irq_err3 Byte framing or EOF error Indicates framing error

Collision error for ISO14443A and ISO15693 single

subcarrier. Bit is set if more then 6 or 7 (as defined in

B1 Irq_col Collision error register 0x01) are detected inside one bit period of

ISO14443A 106 kbps. Collision error bit can also be

triggered by external noise.

No response within the "No-response time" defined in RX

B0 Irq_noresp No-response time interrupt No-response Wait Time register (0x07). Signals the MCU

that next slot command can be sent. Only for ISO15693.

(1) Displays the cause of IRQ and TX/RX status

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6.12.2 Initiator

The chip is fully controlled by the MCU as in RFID reader operation. The MCU activates the chip and

writes the mode selection in the ISO Control register. The MCU uses RF collision avoidance commands,

so it is relieved of any real-time task. The normal transmit and receive procedure (through the FIFO) are

used to communicate with the TARGET device as described in Section 6.10.

6.13 Direct Commands from MCU to Reader

6.13.1 Command Codes

Table 6-19. Address and Command Word Bit Distribution

Command Code Command Comments

0x00 Idle

0x03 Software Initialization Same as Power on Reset

0x04 Perform RF Collision Avoidance

0x05 Perform response RF Collision Avoidance

0x06 Perform response RF Collision Avoidance (n = 0)

0x0F Reset

0x10 Transmission without CRC

0x11 Transmission with CRC

0x12 Delayed Transmission without CRC

0x13 Delayed Transmission with CRC

0x14 End of Frame/Transmit Next Time Slot ISO15693

0x15 Close Slot Sequence

0x16 Block Receiver

0x17 Enable Receiver

0x18 Test internal RF (RSSI at RX input with TX off)

0x19 Test external RF (RSSI at RX input with TX on)

0x1A Receiver Gain Adjust

The command code values from Table 6-19 are substituted in Table 6-20, Bits 0 through 4. Also, the

most-significant bit (MSB) in Table 6-20 must be set to 1. ( Table 6-20 is same as Table 6-11, shown here

again for user clarity).

Table 6-20. Address and Command Word Bit Distribution

Bit Description Bit Function Address Command

0 = address

B7 Command control bit 0 1

1 = command

0 = write

B6 Read/Write R/W 0

1 = read

B5 Continuous address mode 1 = Continuous mode R/W 0

B4 Address/Command bit 4 Adr 4 Cmd 4

B3 Address/Command bit 3 Adr 3 Cmd 3

B2 Address/Command bit 2 Adr 2 Cmd 2

B1 Address/Command bit 1 Adr 1 Cmd 1

B0 Address/Command bit 0 Adr 0 Cmd 0

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The MSB determines if the word is to be used as a command or address. The last two columns of

Table 6-20 show the function of each bit, depending on whether address or command is written.

Command mode is used to enter a command resulting in reader action (initialize transmission, enable

reader, and turn reader on or off).

6.13.1.1 Idle (0x00)

This command issues dummy clock cycles. In parallel mode, one cycle is issued. In SPI mode, eight

cycles are issued.

6.13.1.2 Software Initialization (0x03)

This command starts a Power on Reset. After sending this command, the register values change as

shown in Table 6-21.

Table 6-21. Register Values After Sending Software

Initialization (0x03)

Address Register Value

0x00 Chip Status Control 0x01

0x01 ISO Control 0x21(1)

0x02 ISO14443B TX options 0x00

0x03 ISO14443A high bit rate options 0x00

0x04 TX timer setting, H-byte 0xC1(1)

0x05 TX timer setting, L-byte 0xC1(1)

0x06 TX pulse-length control 0x00

0x07 RX no response wait 0x0E

0x08 RX wait time 0x07(1)

0x09 Modulator and SYS_CLK control 0x91

0x0A RX Special Setting 0x10(1)

0x0B Regulator and I/O control 0x87

0x0C IRQ status 0x00

0x0D Collision position and interrupt mask 0x3E

0x0E Collision position 0x00

0x0F RSSI levels and oscillator status 0x40

0x10 Special Function 0x00

0x11 Special Function 0x00

0x12 RAM 0x00

0x13 RAM 0x00

0x14 Adjustable FIFO IRQ Levels 0x00

0x15 Reserved 0x00

0x16 NFC Low Field Detection Level 0x00

0x18 NFC Target Detection Level 0x00

0x19 NFC Target Protocol 0x00

0x1A Test 0x00

0x1B Test 0x00

0x1C FIFO status 0x00

(1) Differs from default at POR

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6.13.1.3 Initial RF Collision Avoidance (0x04)

This command executes the initial collision avoidance and sends out IRQ after 5 ms from establishing RF

field (so the MCU can start sending commands/data). If the external RF field is present (higher than the

level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on and

hence a different IRQ is returned.

6.13.1.4 Response RF Collision Avoidance (0x05)

This command executes the response collision avoidance and sends out IRQ after 75 µs from establishing

RF field (so the MCU can start sending commands/data). If the external RF field is present (higher than

the level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on

and hence a different IRQ is returned.

6.13.1.5 Response RF Collision Avoidance (0x06, n = 0)

This command executes the response collision avoidance without random delay. It sends out IRQ after 75

µs from establishing RF field (so the MCU can start sending commands/data). If the external RF field is

present (higher than the level set in NFC Low Field Detection Level register (0x16)) then the RF field can

not be switched on and hence a different IRQ is returned.

6.13.1.6 Reset (0x0F)

The reset command clears the FIFO contents and FIFO status register (0x1C). It also clears the register

storing the collision error location (0x0E).

6.13.1.7 Transmission With CRC (0x11)

The transmission command must be sent first, followed by transmission length bytes, and FIFO data. The

reader starts transmitting after the first byte is loaded into the FIFO. The CRC byte is included in the

transmitted sequence.

6.13.1.8 Transmission Without CRC (0x10)

Same as Section 6.13.1.7 with CRC excluded.

6.13.1.9 Delayed Transmission With CRC (0x13)

The transmission command must be sent first, followed by the transmission length bytes, and FIFO data.

The reader transmission is triggered by the TX timer.

6.13.1.10 Delayed Transmission Without CRC (0x12)

Same as Section 6.13.1.9 with CRC excluded.

6.13.1.11 Transmit Next Time Slot (0x14)

When this command is received, the reader transmits the next slot command. The next slot sign is defined

by the protocol selection.

6.13.1.12 Block Receiver (0x16)

The block receiver command puts the digital part of receiver (bit decoder and framer) in reset mode. This

is useful in an extremely noisy environment, where the noise level could otherwise cause a constant

switching of the subcarrier input of the digital part of the receiver. The receiver (if not in reset) would try to

catch a SOF signal, and if the noise pattern matched the SOF pattern, an interrupt would be generated,

falsely signaling the start of an RX operation. A constant flow of interrupt requests can be a problem for

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the external system (MCU), so the external system can stop this by putting the receive decoders in reset

mode. The reset mode can be terminated in two ways. The external system can send the enable receiver

command. The reset mode is also automatically terminated at the end of a TX operation. The receiver can

stay in reset after end of TX if the RX wait time register (0x08) is set. In this case, the receiver is enabled

at the end of the wait time following the transmit operation.

6.13.1.13 Enable Receiver (0x17)

This command clears the reset mode in the digital part of the receiver if the reset mode was entered by

the block receiver command.

6.13.1.14 Test Internal RF (RSSI at RX Input With TX ON) (0x18)

The level of the RF carrier at RF_IN1 and RF_IN2 inputs is measured. Operating range between 300 mVP

and 2.1 VP(step size is 300 mV). The two values are displayed in the RSSI levels register (0x0F). The

command is intended for diagnostic purposes to set correct RF_IN levels. Optimum RFIN input level is

approximately 1.6 VPor code 5 to 6. The nominal relationship between the RF peak level and RSSI code

is shown in Table 6-22 and in Section 6.5.1.1.

NOTE

If the command is executed immediately after power-up and before any communication with

a tag is performed, the command must be preceded by Enable RX command. The Check RF

commands require full operation, so the receiver must be activated by Enable RX or by a

normal Tag communication for the Check RF command to work properly.

Table 6-22. Test Internal RF Peak Level to RSSI Codes

RF_IN1 [mVPP]300 600 900 1200 1500 1800 2100

Decimal Code 1234567

Binary Code 001 010 011 001 101 011 111

6.13.1.15 Test External RF (RSSI at RX Input with TX OFF) (0x19)

This command can be used in active mode when the RF receiver is switched on but RF output is switched

off. This means bit B1 = 1 in Chip Status Control Register. The level of RF signal received on the antenna

is measured and displayed in the RSSI Levels register (0x0F). The relation between the 3 bit code and the

external RF field strength [A/m] must be determinate by calculation or by experiments for each antenna

type as the antenna Q and connection to the RF input influence the result. The nominal relation between

the RF peak to peak voltage in the RF_IN1 input and RSSI code is shown in Table 6-23 and in

Section 6.5.1.2.

NOTE

If the command is executed immediately after power-up and before any communication with

a tag is performed, the command must be preceded by an Enable RX command. The Check

RF commands require full operation, so the receiver must be activated by Enable RX or by a

normal Tag communication for the Check RF command to work properly.

Table 6-23. Test External RF Peak Level to RSSI Codes

RF_IN1 [mVPP]40 60 80 100 140 180 300

Decimal Code 1234567

Binary Code 001 010 011 001 101 011 111

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6.13.1.16 Receiver Gain Adjust (0x1A)

This command should be executed when the MCU determines that no TAG response is coming and when

the RF and receivers are switched ON. When this command is received, the reader observes the digitized

receiver output. If more than two edges are observed in 100 ms, the window comparator voltage is

increased. The procedure is repeated until the number of edges (changes of logical state) of the digitized

reception signal is less than 2 (in 100 ms). The command can reduce the input sensitivity in 5-dB

increments up to 15 dB. This command ensures better operation in a noisy environment. The gain setting

is reset to maximum gain at EN = 0 and POR = 1.

6.14 Register Description

6.14.1 Register Preset

After power-up and the EN pin low-to-high transition, the reader is in the default mode. The default

configuration is ISO15693, single subcarrier, high data rate, 1-out-of-4 operation. The low-level option

registers (0x02 to 0x0B) are automatically set to adapt the circuitry optimally to the appropriate protocol

parameters. When entering another protocol (by writing to the ISO Control register 0x01), the low-level

option registers (0x02 to 0x0B) are automatically configured to the new protocol parameters. After

selecting the protocol, it is possible to change some low-level register contents if needed. However,

changing to another protocol and then back, reloads the default settings, and so then the custom settings

must be reloaded.

The Clo0 and Clo1 register (0x09) bits, which define the microcontroller frequency available on the

SYS_CLK pin, are the only two bits in the configuration registers that are not cleared during protocol

selection.

6.14.2 Register Overview

Table 6-24. Register Definitions

Address Register Read/Write

Main Control Registers

0x00 Chip Status Control R/W

0x01 ISO Control R/W

Protocol Sub-Setting Registers

0x02 ISO14443B TX options R/W

0x03 ISO14443A high bit rate options R/W

0x04 TX timer setting, H-byte R/W

0x05 TX timer setting, L-byte R/W

0x06 TX pulse-length control R/W

0x07 RX no response wait R/W

0x08 RX wait time R/W

0x09 Modulator and SYS_CLK control R/W

0x0A RX Special Setting R/W

0x0B Regulator and I/O control R/W

0x10 Special Function Register, Preset 0x00 R/W

0x11 Special Function Register, Preset 0x00 R/W

0x14 Adjustable FIFO IRQ Levels Register R/W

0x15 Reserved R/W

0x16 NFC Low Field Detection Level R/W

0x17 NFCID1 Number (up to 10 bytes wide) W

0x18 NFC Target Detection Level R/W

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Table 6-24. Register Definitions (continued)

Address Register Read/Write

0x19 NFC Target Protocol R/W

Status Registers

0x0C IRQ status R

0x0D Collision position and interrupt mask register R/W

0x0E Collision position R

0x0F RSSI levels and oscillator status R

RAM

0x12 RAM R/W

0x13 RAM R/W

Test Registers

0x1A Test Register. Preset 0x00 R/W

0x1B Test Register. Preset 0x00 R/W

FIFO Registers

0x1C FIFO status R

0x1D TX length byte 1 R/W

0x1E TX length byte 2 R/W

0x1F FIFO I/O register R/W

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6.14.3 Detailed Register Description

6.14.3.1 Main Configuration Registers

6.14.3.1.1 Chip Status Control Register (0x00)

Table 6-25. Chip Status Control Register (0x00)

Function: Control of Power mode, RF on/off, AGC, AM/PM, Direct Mode

Default: 0x01, preset at EN = L or POR = H

Bit Name Function Description

Standby mode keeps all supply regulators, 13.56-MHz SYS_CLK oscillator

1 = Standby Mode running. (typical start-up time to full operation 100 µs)

B7 stby

0 = Active Mode Active Mode (default)

Provides user direct access to AFE (Direct Mode 0) or allows user to add their

1 = Direct Mode 0 or 1 own framing (Direct Mode 1). Bit 6 of ISO Control register must be set by user

B6 direct before entering Direct Mode 0 or 1.

0 = Direct Mode 2 (default) Uses SPI or parallel communication with automatic framing and ISO decoders

1 = RF output active Transmitter on, receivers on

B5 rf_on 0 = RF output not active Transmitter off

TX_OUT (pin 5) = 8-Ωoutput impedance P = 100 mW (20 dBm) at 5 V,

1 = half output power P = 33 mW (+15 dBm) at 3.3 V

B4 rf_pwr TX_OUT (pin 5) = 4-Ωoutput impedance P = 200 mW (+23 dBm) at 5 V,

0 = full output power P = 70 mW (+18 dBm) at 3.3 V

1 = selects Aux RX input RX_IN2 input is used

B3 pm_on 0 = selects Main RX input RX_IN1 input is used

1 = AGC on Enables AGC (AGC gain can be set in register 0x0A)

B2 agc_on 0 = AGC off AGC block is disabled

1 = Receiver activated for Forced enabling of receiver and TX oscillator. Used for external field

external field measurement measurement.

B1 rec_on

0 = Automatic Enable Allows enable of the receiver by Bit 5 of this register (0x00)

1 = 5 V operation

B0 vrs5_3 Selects the VIN voltage range

0 = 3 V operation

6.14.3.1.2 ISO Control Register (0x01)

Table 6-26. ISO Control Register (0x01)

Function: Controls the selection of ISO Standard protocol, Direct Mode and Receive CRC

Default: 0x02 (ISO15693 high bit rate, one subcarrier, 1 out of 4); it is preset at EN = L or POR = H

Bit Name Function Description

0 = RX CRC (CRC is present in the response)

B7 rx_crc_n CRC Receive selection 1 = no RX CRC (CRC is not present in the response)(1)

0 = Direct Mode 0

B6 dir_mode Direct mode type selection 1 = Direct Mode 1

0 = RFID Mode

B5 rfid RFID / Reserved 1 = NFC or Card Emulation Mode

RFID: See Table 6-27 for B0:B4 settings based on ISO protocol desired by

application

B4 iso_4 RFID / NFC Target NFC:

0 = target

1 = initiator

NFC:

B3 iso_3 RFID / NFC Mode 0 = passive mode

1 = active mode

(1) Only applicable to ISO-14443A and ISO-15693

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Table 6-26. ISO Control Register (0x01) (continued)

NFC:

B2 iso_2 RFID / Card Emulation 0 = NFC Normal Modes

1 = Card Emulation Mode

NFC:

B1 iso_1 RFID / NFC bit rate 0 = bit rate selection or card emulation selection, see Table 6-28

NFC:

B0 iso_0 RFID / NFC bit rate 0 = bit rate selection or card emulation selection, see Table 6-28

Table 6-27. ISO Control Register ISO_x Settings, RFID Mode

ISO_4 ISO_3 ISO_2 ISO_1 ISO_0 Protocol Remarks

0 0 0 0 0 ISO15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 4

0 0 0 0 1 ISO15693 low bit rate, 6.62 kbps, one subcarrier, 1 out of 256

0 0 0 1 0 ISO15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 4 Default for reader

0 0 0 1 1 ISO15693 high bit rate, 26.48 kbps, one subcarrier, 1 out of 256

0 0 1 0 0 ISO15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of 4

0 0 1 0 1 ISO15693 low bit rate, 6.67 kbps, double subcarrier, 1 out of 256

0 0 1 1 0 ISO15693 high bit rate, 26.69 kbps, double subcarrier, 1 out of 4

ISO15693 high bit rate, 26.69 kbps, double subcarrier,

001111 out of 256

0 1 0 0 0 ISO14443A RX bit rate, 106 kbps RX bit rate (1)

0 1 0 0 1 ISO14443A RX high bit rate, 212 kbps

0 1 0 1 0 ISO14443A RX high bit rate, 424 kbps

0 1 0 1 1 ISO14443A RX high bit rate, 848 kbps

0 1 1 0 0 ISO14443B RX bit rate, 106 kbps RX bit rate (1)

0 1 1 0 1 ISO14443B RX high bit rate, 212 kbps

0 1 1 1 0 ISO14443B RX high bit rate, 424 kbps

0 1 1 1 1 ISO14443B RX high bit rate, 848 kbps

1 0 0 1 1 Reserved

1 0 1 0 0 Reserved

1 1 0 1 0 FeliCa 212 kbps

1 1 0 1 1 FeliCa 424 kbps

(1) For ISO14443A/B, when bit rate of TX is different from RX, settings can be done in register 0x02 or 0x03.

Table 6-28. ISO Control Register ISO_x Settings,

NFC Mode (B5 = 1, B2 = 0) or Card Emulation (B5 = 1, B2 = 1)

NFC Card Emulation

ISO_1 ISO_0 (B5 = 1, B2 = 0) (B5 = 1, B2 = 1)

0 0 N/A ISO14443A

0 1 106 kbps ISO14443B

1 0 212 kbps N/A

1 1 424 kbps N/A

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6.14.3.2 Control Registers – Sub Level Configuration Registers

6.14.3.2.1 ISO14443 TX Options Register (0x02)

Table 6-29. ISO14443 TX Options Register (0x02)

Function: Selects the ISO subsets for ISO14443 – TX

Default: 0x00 at POR = H or EN = L

Bit Name Function Description

B7 egt2 TX EGT time select MSB Three bit code defines the number of etu (0-7) which separate two characters.

B6 egt1 TX EGT time select ISO14443B TX only.

B5 egt0 TX EGT time select LSB

1 = EOF→0 length 11 etu

B4 eof_l0 0 = EOF→0 length 10 etu

1 = SOF→1 length 03 etu

B3 sof_l1 0 = SOF→1 length 02 etu

ISO14443B TX only

1 = SOF→0 length 11 etu

B2 sof _l0 0 = SOF→0 length 10 etu

1 = EGT after each byte

B1 l_egt 0 = EGT after last byte is

omitted

1 = ISO14443A Layer 4

compliant (in SAK For use with Auto SDD configuration, makes B6 in ISO14443A response 1 or 0,

B0 Auto SDD_SAK response) indicating Layer 4 compliance (or not), for all other cases, this bit is unused

0 = Not Layer 4 compliant

(in SAK response)

6.14.3.2.2 ISO14443 High-Bit-Rate and Parity Options Register (0x03)

Table 6-30. ISO14443 High-Bit-Rate and Parity Options Register (0x03)

Function: Selects the ISO subsets for ISO14443 – TX

Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register

Bit Name Function Description

TX bit rate different from RX

B7 dif_tx_br Valid for ISO14443A/B high bit rate

bit rate enable

B6 tx_br1 tx_br1 = 0, tx_br = 0 →106 kbps

tx_br1 = 0, tx_br = 1 →212 kbps

TX bit rate tx_br1 = 1, tx_br = 0 →424 kbps

B5 tx_br0 tx_br1 = 1, tx_br = 1 →848 kbps

1 = parity odd except last

B4 parity-2tx byte which is even for TX For 14443A high bit rate, coding and decoding

1 = parity odd except last

B3 parity-2rx byte which is even for RX

B2 Unused

B1 Unused

B0 Unused

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6.14.3.2.3 TX Timer High Byte Control Register (0x04)

Table 6-31. TX Timer High Byte Control Register (0x04)

Function: For Timings

Default: 0xC2 at POR = H or EN = L, and at each write to ISO Control register

Bit Name Function Description

B7 tm_st1 Timer Start Condition tm_st1 = 0, tm_st0 = 0 →beginning of TX SOF

tm_st1 = 0, tm_st0 = 1 →end of TX SOF

tm_st1 = 1, tm_st0 = 0 →beginning of RX SOF

B6 tm_st0 Timer Start Condition tm_st1 = 1, tm_st0 = 1 →end of RX SOF

B5 tm_lengthD Timer Length MSB

B4 tm_lengthC Timer Length

B3 tm_lengthB Timer Length

B2 tm_lengthA Timer Length

B1 tm_length9 Timer Length

B0 tm_length8 Timer Length LSB

6.14.3.2.4 TX Timer Low Byte Control Register (0x05)

Table 6-32. TX Timer Low Byte Control Register (0x05)

Function: For Timings

Default: 0x00 at POR = H or EN = L, and at each write to ISO Control register

Bit Name Function Description

B7 tm_length7 Timer Length MSB

B6 tm_length6 Timer Length Defines the time when delayed transmission is started.

B5 tm_length5 Timer Length RX wait range is 590 ns to 9.76 ms (1 to 16383)

B4 tm_length4 Timer Length Step size is 590 ns

B3 tm_length3 Timer Length

All bits low = timer disabled (0x00)

B2 tm_length2 Timer Length

B1 tm_length1 Timer Length Preset 0x00 for all other protocols

B0 tm_length0 Timer Length LSB

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6.14.3.2.5 TX Pulse Length Control Register (0x06)

The length of the modulation pulse is defined by the protocol selected in the ISO Control register 0x01.

With a high Q antenna, the modulation pulse is typically prolonged, and the tag detects a longer pulse

than intended. For such cases, the modulation pulse length can be corrected by using the TX Pulse

Length Control register (0x06). If the register contains all zeros, then the pulse length is governed by the

protocol selection. If the register contains a value other than 0x00, the pulse length is equal to the value of

the register in 73.7-ns increments. This means the range of adjustment can be 73.7 ns to 18.8 µs.

Table 6-33. TX Pulse Length Control Register (0x06)

Function: Controls the length of TX pulse

Default: 0x00 at POR = H or EN = L and at each write to ISO Control register.

Bit Name Function Description

B7 Pul_p2 Pulse length MSB The pulse range is 73.7 ns to 18.8 µs (1….255), step size 73.7 ns.

B6 Pul_p1 All bits low (00): pulse length control is disabled.

B5 Pul_p0 The following default timings are preset by the ISO Control register (0x01):

B4 Pul_c4

9.44 µs →ISO15693 (TI Tag-It HF-I)

B3 Pul_c3

B2 Pul_c2 11 µs →Reserved

B1 Pul_c1 2.36 µs →ISO14443A at 106 kbps

1.4 µs →ISO14443A at 212 kbps

B0 Pul_c0 Pulse length LSB 737 ns →ISO14443A at 424 kbps

442 ns →ISO14443A at 848 kbps; pulse length control disabled

6.14.3.2.6 RX No Response Wait Time Register (0x07)

The RX No Response timer is controlled by the RX NO Response Wait Time Register 0x07. This timer

measures the time from the start of slot in the anticollision sequence until the start of tag response. If there

is no tag response in the defined time, an interrupt request is sent and a flag is set in IRQ status control

wait time is stored in the register in increments of 37.76 µs. This register is also preset, automatically, for

every new protocol selection. Sending a Reset FIFO (0x0F) direct command after a TX Complete interrupt

will disable this feature.

Table 6-34. RX No Response Wait Time Register (0x07)

Function: Defines the time when "no response" interrupt is sent; only for ISO15693

Default: 0x0E at POR = H or EN = L and at each write to ISO Control register

Bit Name Function Description

B7 NoResp7 No response MSB Defines the time when "no response" interrupt is sent. It starts from the end of

B6 NoResp6 TX EOF. RX no response wait range is 37.76 µs to 9628 µs (1 to 255), step

size is: 37.76 µs.

B5 NoResp5

The following default timings are preset by the ISO Control register (0x01):

B4 NoResp4

B3 NoResp3 390 µs →Reserved

B2 NoResp2 529 µs →for all protocols supported, but not listed here

B1 NoResp1 604 µs →Reserved

755 µs →ISO15693 high data rate (TI Tag-It HF-I)

B0 NoResp0 No response LSB

1812 µs →ISO15693 low data rate (TI Tag-It HF-I)

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6.14.3.2.7 RX Wait Time Register (0x08)

The RX-wait-time timer is controlled by the value in the RX wait time register 0x08. This timer defines the

time after the end of the transmit operation in which the receive decoders are not active (held in reset

state). This prevents incorrect detections resulting from transients following the transmit operation. The

value of the RX wait time register defines this time in increments of 9.44 µs. This register is preset at

every write to ISO Control register 0x01 according to the minimum tag response time defined by each

standard.

Table 6-35. RX Wait Time Register (0x08)

Function: Defines the time after TX EOF when the RX input is disregarded for example, to block out electromagnetic disturbance

generated by the responding card.

Default: 0x1F at POR = H or EN = L and at each write toISO control register.

Bit Name Function Description

B7 Rxw7 Defines the time after the TX EOF during which the RX input is ignored. Time

B6 Rxw6 starts from the end of TX EOF.

B5 Rxw5 RX wait range is 9.44 µs to 2407 µs (1 to 255), Step size 9.44 µs.

B4 Rxw4 The following default timings are preset by the ISO Control register (0x01):

RX wait time

B3 Rxw3 9.44 µs →FeliCa

B2 Rxw2 66 µs →ISO14443A and B

B1 Rxw1

180 µs →Reserved

B1 Rxw0 293 µs →ISO15693 (TI Tag-It HF-I)

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6.14.3.2.8 Modulator and SYS_CLK Control Register (0x09)

The frequency of SYS_CLK (pin 27) is programmable by the bits B4 and B5 of this register. The frequency

of the TRF7970A system clock oscillator is divided by 1, 2 or 4 resulting in available SYS_CLK

frequencies of 13.56 MHz or 6.78 MHz or 3.39 MHz.

The ASK modulation depth is controlled by bits B0, B1 and B2. The range of ASK modulation is 7% to

30% or 100% (OOK). The selection between ASK and OOK (100%) modulation can also be done using

direct input OOK (pin 12). The direct control of OOK/ASK using OOK pin is only possible if the function is

enabled by setting B6 = 1 (en_ook_p) in this register (0x09) and the ISO Control Register (0x01, B6 = 1).

When configured this way, the MOD (pin 14) is used as input for the modulation signal.

Table 6-36. Modulator and SYS_CLK Control Register (0x09)

Function: Controls the modulation input and depth, ASK / OOK control and clock output to external system (MCU)

Default: 0x91 at POR = H or EN = L, and at each write to ISO control register, except Clo1 and Clo0.

Bit Name Function Description

B7 27MHz Enables 27.12-MHz crystal Default = 1 (enabled)

Enable ASK/OOK pin (pin 12) for "on the fly change" between any preselected

1 = Enables external ASK modulation as defined by B0 to B2 and OOK modulation:

selection of ASK or OOK

B6 en_ook_p modulation If B6 is 1, pin 12 is configured as follows:

0 = Default operation as 1 = OOK modulation

defined in B0 to B2 (0x09)

0 = Modulation as defined in B0 to B2 (0x09)

SYS_CLK Output SYS_CLK Output

Clo1 Clo0 (if 13.56-MHz (if 27.12-MHz

SYS_CLK output frequency crystal is used) crystal is used)

B5 Clo1 MSB 0 0 Disabled Disabled

0 1 3.39 MHz 6.78 MHz

1 0 6.78 MHz 13.56 MHz

SYS_CLK output frequency

B4 Clo0 LSB 1 1 13.56 MHz 27.12 MHz

1 = Sets pin 12 (ASK/OOK) For test and measurement purpose. ASK/OOK pin 12 can be used to monitor

B3 en_ana as an analog output the analog subcarrier signal before the digitizing with DC level equal to AGND.

0 = Default

Pm2 Pm1 Pm0 Mod Type and %

B2 Pm2 Modulation depth MSB 0 0 0 ASK 10%

0 0 1 OOK (100%)

0 1 0 ASK 7%

B1 Pm1 Modulation depth 0 1 1 ASK 8.5%

1 0 0 ASK 13%

1 0 1 ASK 16%

B0 Pm0 Modulation depth LSB 1 1 0 ASK 22%

1 1 1 ASK 30%

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6.14.3.2.9 RX Special Setting Register (Address 0x0A)

Table 6-37. RX Special Setting Register (Address 0x0A)

Function: Sets the gains and filters directly

Default: 0x40 at POR = H or EN = L, and at each write to the ISO Control register 0x01. When bits B7, B6, B5 and B4 are all zero, the

filters are set for ISO14443B (240 kHz to 1.4 MHz).

Bit Name Function Description

B7 C212 Bandpass 110 kHz to 570 kHz Appropriate for 212-kHz subcarrier system (FeliCa)

B6 C424 Bandpass 200 kHz to 900 kHz Appropriate for 424-kHz subcarrier used in ISO15693

Appropriate for Manchester-coded 848-kHz subcarrier used in ISO14443A

B5 M848 Bandpass 450 kHz to 1.5 MHz and B

Bandpass 100 kHz to 1.5 MHz

B4 hbt Appropriate for highest bit rate (848 kbps) used in high-bit-rate ISO14443

Gain reduced for 18 dB

B3 gd1 00 = Gain reduction 0 dB

01 = Gain reduction for 5 dB Sets the RX gain reduction, and reduces sensitivity

10 = Gain reduction for 10 dB

B2 gd2 11 = Gain reduction for 15 dB

AGC activation level changed from five times the digitizing level to three

times the digitizing level.

B1 agcr AGC activation level change 1 = 3x

0 = 5x

AGC action can be done any time during receive process. It is not limited

to the start of receive ("max hold").

B0 no-lim AGC action is not limited in time 1 = continuously – no time limit

0 = 8 subcarrier pulses

The first four steps of the AGC control are comparator adjustment. The second three steps are real gain

reduction done automatically by AGC control. The AGC is turned on after TX.

The first gain and filtering stage following the RF envelope detector has a nominal gain of 15 and the 3-dB

band-pass frequencies are adjustable in the range from 100 kHz to 400 kHz for high pass and 600 kHz to

1.5 MHz for low pass. The next gain and filtering stage has a nominal gain of 8 and the frequency

characteristic identical to first stage. The filter setting is done automatically with internal preset for each

new selection of communication standard in ISO Control register (0x01). Additional corrections can be

done by directly writing into the RX Special Setting register 0x0A.

The second receiver gain stage and digitizer stage are included in the AGC loop. The AGC loop can be

activated by setting the bit B2 = 1 (agc-on) in Chip Status Control register 0x00. If activated the AGC

monitors the signal level at the input of digitizing stage. If the signal level is significantly higher than the

digitizing threshold level, the gain reduction is activated. The signal level, at which the action is started, is

by default five times the digitizing threshold level. It can be reduced to three times the digitizing level by

setting bit B1 = 1 (agcr) in RX Special Setting register (0x0A).

The AGC action is fast and it typically finishes within eight subcarrier pulses. By default the AGC action is

blocked after first few pulses of subcarrier signal so AGC cannot interfere with signal reception during rest

of data packet. In certain cases, this is not optimal, so this blocking can be removed by setting B0 = 1

(no_lim) in RX Special Setting register (0x0A).

NOTE

The setting of bits B4, B5, B6 and B7 to zero selects bandpass characteristic of 240 kHz to

1.4 MHz. This is appropriate for ISO14443B, FeliCa protocol, and ISO14443A higher bit

rates 212 kbps and 424 kbps.

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6.14.3.2.10 Regulator and I/O Control Register (0x0B)

Table 6-38. Regulator and I/O Control Register (0x0B)

Function: Control the three voltage regulators

Default: 0x87 at POR = H or EN = L

Bit Name Function Description

0 = Manual settings; see B0

to B2 in Table 6-39 and Auto system sets VDD_RF = VIN – 250 mV and VDD_A = VIN – 250 mV and

B7 auto_reg Table 6-40 VDD_X= VIN – 250 mV, but not higher than 3.4 V.

1 = Automatic setting

Internal peak detectors are disabled, receiver inputs (RX_IN1 and RX_IN2)

Support for external power

B6 en_ext_pa accept externally demodulated subcarrier. At the same time ASK/OOK pin 12

amplifier becomes modulation output for external TX amplifier.

When B5 = 1, maintains the output driving capabilities of the I/O pins connected

1 = enable low peripheral

B5 io_low to the level shifter under low voltage operation. Should be set 1 when VDD_I/O

communication voltage voltage is between 1.8 V to 2.7 V.

B4 Unused No function Default is 0.

B3 Unused No function Default is 0.

B2 vrs2 Voltage set MSB voltage Vrs3_5 = L: VDD_RF, VDD_A, VDD_X range 2.7 V to 3.4 V; see Table 6-39 and

B1 vrs1 set LSB Table 6-40

B0 vrs0

Table 6-39. Supply-Regulator Setting – Manual 5-V System

Option Bits Setting in Control Register

B7 B6 B5 B4 B3 B2 B1 B0

00 1 5-V system

0B 0 Manual regulator setting

0B 0 1 1 1 VDD_RF = 5 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 1 1 0 VDD_RF = 4.9 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 1 0 1 VDD_RF = 4.8 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 1 0 0 VDD_RF = 4.7 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 0 1 1 VDD_RF = 4.6 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 0 1 0 VDD_RF = 4.5 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 0 0 1 VDD_RF = 4.4 V, VDD_A = 3.4 V, VDD_X = 3.4 V

0B 0 0 0 0 VDD_RF = 4.3 V, VDD_A = 3.4 V, VDD_X = 3.4 V

Table 6-40. Supply-Regulator Setting – Manual 3-V System

Option Bits Setting in Control Register

B7 B6 B5 B4 B3 B2 B1 B0

00 0 3-V system

0B 0 Manual regulator setting

0B 0 1 1 1 VDD_RF = 3.4 V, VDD_A and VDD_X = 3.4 V

0B 0 1 1 0 VDD_RF = 3.3 V, VDD_A and VDD_X = 3.3 V

0B 0 1 0 1 VDD_RF = 3.2 V, VDD_A and VDD_X = 3.2 V

0B 0 1 0 0 VDD_RF = 3.1 V, VDD_A and VDD_X = 3.1 V

0B 0 0 1 1 VDD_RF = 3.0 V, VDD_A and VDD_X = 3.0 V

0B 0 0 1 0 VDD_RF = 2.9 V, VDD_A and VDD_X = 2.9 V

0B 0 0 0 1 VDD_RF = 2.8 V, VDD_A and VDD_X = 2.8 V

0B 0 0 0 0 VDD_RF = 2.7 V, VDD_A and VDD_X = 2.7 V

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Table 6-41. Supply-Regulator Setting – Automatic 5-V System

Option Bits Setting in Control Register

B7 B6 B5 B4 B3 B2 B1 B0

00 1 5-V system

0B 1 x(1) 0 0 Automatic regulator setting 400-mV difference

(1) x = don't care

Table 6-42. Supply-Regulator Setting – Automatic 3-V System

Option Bits Setting in Control Register

B7 B6 B5 B4 B3 B2 B1 B0

00 0 3-V system

0B 1 x(1) 0 0 Automatic regulator setting 400-mV difference

(1) x = don't care

6.14.3.3 Status Registers

6.14.3.3.1 IRQ Status Register (0x0C)

Table 6-43. IRQ Status Register (0x0C)

Function: Information available about TRF7970A IRQ and TX/RX status

Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read

phase. The reset also removes the IRQ flag.

Bit Name Function Description

Signals that TX is in progress. The flag is set at the start of TX but the interrupt

B7 Irq_tx IRQ set due to end of TX request (IRQ = 1) is sent when TX is finished.

Signals that RX SOF was received and RX is in progress. The flag is set at the

B6 Irg_srx IRQ set due to RX start start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.

Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)

B5 Irq_fifo Signals the FIFO level register

Indicates receive CRC error only if B7 (no RX CRC) of ISO Control register is

B4 Irq_err1 CRC error set to 0.

B3 Irq_err2 Parity error Indicates parity error for ISO14443A

B2 Irq_err3 Byte framing or EOF error Indicates framing error

Collision error for ISO14443A and ISO15693 single subcarrier. Bit is set if more

then 6 or 7 (as defined in register 0x01) are detected inside one bit period of

B1 Irq_col Collision error ISO14443A 106 kbps. Collision error bit can also be triggered by external

noise.

No response within the "No-response time" defined in RX No-response Wait

B0 Irq_noresp No-response time interrupt Time register (0x07). Signals the MCU that next slot command can be sent.

Only for ISO15693.

To reset (clear) the register 0x0C and the IRQ line, the register must be read. During Transmit the

decoder is disabled, only bits B5 and B7 can be changed. During Receive only bit B6 can be changed, but

does not trigger the IRQ line immediately. The IRQ signal is set at the end of Transmit and Receive

phase.

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Table 6-44. IRQ Status Register (0x0C) for NFC and Card Emulation Operation

Function: Information available about TRF7970A IRQ and TX/RX status

Default: 0x00 at POR = H or EN = L, and at each write to the ISO Control Register 0x01. It is also automatically reset at the end of a read

phase. The reset also removes the IRQ flag.

Bit Name Function Description

Signals that TX is in progress. The flag is set at the start of TX but the interrupt

B7 Irq_tx IRQ set due to end of TX request (IRQ = 1) is sent when TX is finished.

Signals that RX SOF was received and RX is in progress. The flag is set at the

B6 Irg_srx IRQ set due to RX start start of RX but the interrupt request (IRQ = 1) is sent when RX is finished.

Signals FIFO high or low as set in the Adjustable FIFO IRQ Levels (0x14)

B5 Irq_fifo Signals the FIFO level register

B4 Irq_err1 Protocol error Any protocol error

B3 Irq_sdd SDD completed SDD (passive target at 106 kbps) successfully finished

B2 Irq_rf RF field change Sufficient RF signal level for operation was reached or lost

RF collision avoidance The system has finished collision avoidance and the minimum wait time is

B1 Irq_col finished elapsed.

RF collision avoidance not The external RF field was present so the collision avoidance could not be

B0 Irq_col_err finished successfully carried out.

6.14.3.3.2 Interrupt Mask Register (0x0D) and Collision Position Register (0x0E)

Table 6-45. Interrupt Mask Register (0x0D)

Default: 0x3E at POR = H and EN = L. Collision bits reset automatically after read operation.

Bit Name Function Description

B7 Col9 Bit position of collision MSB Supports ISO14443A

B6 Col8 Bit position of collision

B5 En_irq_fifo Interrupt enable for FIFO Default = 1

B4 En_irq_err1 Interrupt enable for CRC Default = 1

B3 En_irq_err2 Interrupt enable for Parity Default = 1

Interrupt enable for Framing

B2 En_irq_err3 Default = 1

error or EOF

Interrupt enable for collision

B1 En_irq_col Default = 1

error

Enables no-response

B0 En_irq_noresp Default = 0

interrupt

Table 6-46. Collision Position Register (0x0E)

Function: Displays the bit position of collision or error

Default: 0x00 at POR = H and EN = L. Automatically reset after read operation.

Bit Name Function Description

B7 Col7 Bit position of collision MSB

B6 Col6

B5 Col5

B4 Col4 ISO14443A mainly supported, in the other protocols this register shows the bit

position of error. Either frame, SOF/EOF, parity or CRC error.

B3 Col3

B2 Col2

B1 Col1

B0 Col0 Bit position of collision LSB

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6.14.3.3.3 RSSI Levels and Oscillator Status Register (0x0F)

Table 6-47. RSSI Levels and Oscillator Status Register (0x0F)

Function: Displays the signal strength on both reception channels and RF amplitude during RF-off state. The RSSI values are valid from

reception start till start of next transmission.

Bit Name Function Description

B7 Unused

Crystal oscillator stable

B6 osc_ok 13.56-MHz frequency stable (≈200 µs)

indicator

MSB RSSI value of auxiliary

B5 rssi_x2 Auxiliary channel is by default RX_IN2. The input can be swapped by B3 = 1

RX (RX_IN2) (Chip State Control register 0x00). If "swapped", the Auxiliary channel is

B4 rssi_x1 Auxiliary channel RSSI connected to RX_IN1 and, hence, the Auxiliary RSSI represents the signal level

MSB RSSI value of auxiliary at RX_IN2.

B3 rssi_x0 RX (RX_IN2)

MSB RSSI value of main

B2 rssi_2 RX (RX_IN1) Active channel is default and can be set with option bit B3 = 0 of chip state

B1 rssi_1 Main channel RSSI control register 0x00.

LSB RSSI value of main RX

B0 rssi_0 (RX_IN1)

RSSI measurement block is measuring the demodulated envelope signal (except in case of direct

command for RF amplitude measurement described later in direct commands section). The measuring

system is latching the peak value, so the RSSI level can be read after the end of receive packet. The

RSSI value is reset during next transmit action of the reader, so the new tag response level can be

measured. The RSSI levels calculated to the RF_IN1 and RF_IN2 are presented in Section 6.5.1.1 and

Section 6.5.1.2. The RSSI has 7 steps (3 bits) with 4-dB increment. The input level is the peak to peak

modulation level of RF signal measured on one side envelope (positive or negative).

6.14.3.3.4 Special Functions Register (0x10)

Table 6-48. Special Functions Register (0x10)

Function: User configurable options for ISO14443A specific operations

Bit Name Function Description

B7 Reserved Reserved

B6 Reserved Reserved

Disables parity checking for

B5 par43 ISO14443A

0 = 18.88 µs

B4 next_slot_37us Sets the time grid for next slot command in ISO15693

1 = 37.77 µs

Bit stream transmit for Enables direct mode for transmitting ISO14443A data, bypassing the FIFO and

B3 Sp_dir_mode MIFARE at 106 kbps feeding the data bit stream directly onto the encoder.

0 = normal receive Enable 4-bit replay for example, ACK, NACK used by some cards; for example,

B2 4_bit_RX 1 = 4-bit receive MIFARE Ultralight

0 = anticollision framing

(0x93, 0x95, 0x97) Disable anticollision frames for 14443A (this bit should be set to 1 after

B1 14_anticoll 1 = normal framing (no anticollision is finished)

broken bytes)

0 = 7 subcarrier pulses Selects the number of subcarrier pulses that trigger collision error in the

B0 col_7_6 1 = 6 subcarrier pulses 14443A - 106 kbps

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6.14.3.3.5 Special Functions Register (0x11)

Table 6-49. Special Functions Register (0x11)

Function: Indicate IRQ status for RX operations.

Bit Name Function Description

B7 Reserved Reserved

B6 Reserved Reserved

B5 Reserved Reserved

B4 Reserved Reserved

B3 Reserved Reserved

B2 Reserved Reserved

B1 Reserved Reserved

Copy of the RX start signal Signals the RX SOF was received and the RX is in progress. IRQ when RX is

B0 irg_srx (Bit 6) of the IRQ Status completed.

6.14.3.3.6 Adjustable FIFO IRQ Levels Register (0x14)

Table 6-50. Adjustable FIFO IRQ Levels Register (0x14)

Function: Adjusts level at which FIFO indicates status by IRQ

Default: 0x00 at POR = H and EN = L

Bit Name Function Description

B7 Reserved Reserved

B6 Reserved Reserved

B5 Reserved Reserved

B4 Reserved Reserved

B3 Wlh_1 Wlh_1 Wlh_0 IRQ Level

0 0 124

FIFO high IRQ level (during 0 1 120

RX)

B2 Wlh_0 1 0 112

1 1 96

B1 Wll_1 Wll_1 Wll_0 IRQ Level

004

FIFO low IRQ level (during 018

TX)

B0 Wll_0 1 0 16

1 1 32

6.14.3.3.7 NFC Low Field Level Register (0x16)

Table 6-51. NFC Low Field Level Register (0x16)

Function: Defines level for RF collision avoidance

Default: 0x00 at POR = H and EN = L.

Bit Name Function Description

B7 Clex_dis Disable clock extractor NFC passive 106-kbps and ISO14443A card emulation

B6 Hash6 N/A

B5 Hash5 N/A

B4 Hash4 N/A

B3 Hash3 N/A

B2 Rfdet_I2 RF field level for RF Comparator output is displayed in B6 of the NFC Target Protocol register

B1 Rfdet_I1 collision avoidance (0x19)

B0 Rfdet_I0

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6.14.3.3.8 NFCID1 Number Register (0x17)

This register is used to hold the ID of the TRF7970A for use during card emulation and NFC peer-to-peer

target operations.

The procedure for writing the ID into register 0x17 is the following:

1. Write bits 5, 6, and 7 in register 0x18 to enable SDD anticollision (bit 5), and set bit 6 and 7 to select

the ID length of 4, 7, or 10 bytes.

2. Write the ID into register 0x17. This should be done using write continuous mode with 4, 7, or 10 bytes

(according to what was set in register 0x18 bits 6 and 7).

6.14.3.3.9 NFC Target Detection Level Register (0x18)

Table 6-52. NFC Target Detection Level Register (0x18)

Function: Defines level for RF wake up, enables automatic SDD and gives NFCID size. This register is supplied by Vin to ensure data

retention during complete power down.

Default: 0x00 at POR on Vin (not POR based on VDD_X) and not reset at EN = 0

Bit Name Function Description

NFCID1 Size

Id_s1 Id_s0 (bytes)

B7 Id_s1 004

NFCID1 size used in 106-

kbps passive target SDD 0 1 7

1 0 10

B6 Id_s0 1 1 Not allowed

Automatic SDD using internal state machine and ID stored in the NFCID1

B5 Sdd_en Number register (0x17)

B4 N/A

Extended range for RF

B3 Hi_rf measurements

B2 Rfdet_h2 RF field level required for Comparator output is displayed in B7 of the NFC Target Protocol register

system wakeup. If all bits (0x19)

B1 Rfdet_h1 are 0, then the RF level

B0 Rfdet_h0 detection is off.

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6.14.3.3.10 NFC Target Protocol Register (0x19)

This register is used (when read) to display the bit rate and protocol type when an NFC/RFID

Initiator/Reader is presented. An example use of this scenario would be when the TRF7970A is placed

into card emulation (Type A or Type B) and another TRF7970A or NFC device (polling for other NFC

devices) is presented to the TRF7970A in card emulation mode. The IRQ indicates that a field was

detected (IRQ Status = 0x04) or that Auto SDD has completed (IRQ Status = 0x08, if configured for

AutoSDD).

If Auto SDD is set and 0x04 is returned in IRQ status, then this register can be read out to see which

commands are coming in for gaining knowledge of the polling cycle sequence. Then, when the correct first

matching command (that is, REQA or REQB) is issued from Reader or Initiator, if AutoSDD is set, the IRQ

fires and the IRQ Status is 0x08, indicating completion of the SDD. The next IRQ should return 0x40 as

status, the Register 0x19 can be checked to make sure it is correct value (that is, 0xC9 for Type A at 106

kpbs or 0xC5 for Type B at 106 kbps) indicating there are bytes in the FIFO and a read of the FIFO status

indicates how many bytes to read out. For example, after AutoSDD is completed, there are four bytes in

the FIFO, and these should be the RATS command coming in from the reader, which the MCU controlling

the TRF7970A in Card Emulation mode must respond to. If AutoSDD is not set, as another example with

the TRF7970A in ISO14443B Card Emulation mode, then the field detect happens as previously described

and IRQs also fire to indicate RX is complete (0x40). This register must be checked and compared against

case statement structure that is set up for the value of this register to be 0xC5, indicating that an

ISO14443B command at 106 kbps was issued. When this register (0x19) is 0xC5, then the FIFO Status

can be read and should hold a value of 0x03, and when read, be the REQB command (0x05, 0x00, 0x00);

the controlling MCU must respond with the ATQB response. The next steps for either of these examples

follow the revelent portions of the ISO14443-3 or -4 standards, then the NFC Forum specifications,

depending on the system use case or application.

Table 6-53. NFC Target Protocol Register (0x19)

Function: Displays the bit rate and protocol type (active or passive) transmitted by initiator in first command. It also displays the comparator

outputs of both RF level detectors.

Default: 0x00 at POR = H and EN = L. B0 to B4 are automatically reset after MCU continuous read operation. B6 and B7 continuously

display the RF level comparator outputs.

Bit Name Function Description

RF level is above the wake- The wakeup level is defined by bits B0 to B2 in the NFC Target Detection Level

B7 Rf_h up level setting register (0x18)

RF level is above the RF The collision avoidance level is defined by bits B0 – B2 in the register 0x16

B6 Rf_l collision avoidance level (NFC Low Field Detection Level)

setting

B5 Reserved Reserved Reserved

1 = FeliCa

B4 FeliCa The first initiator command had physical level coding of FeliCa or ISO14443A

0 = ISO14443A

Passive target at 106 kbps

B3 Pas_106 The first initiator/reader command was SENS_REQ or ALL_REQ

or transponder emulation

ISO14443B transponder

B2 Pas_14443B The first reader command was ISO14443B

emulation

B1 NFCBR1 00 = Reserved

Bit rate of first received 01 = 106 kbps

command 10 = 212 kbps

B0 NFCBR0 11 = 424 kbps

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6.14.3.4 Test Registers

6.14.3.4.1 Test Register (0x1A)

Table 6-54. Test Register (0x1A) (for Test or Direct Use)

Default: 0x00 at POR = H and EN = L.

Bit Name Function Description

B7 OOK_Subc_In Subcarrier Input OOK Pin becomes decoder digital input

B6 MOD_Subc_Out Subcarrier Output MOD Pin becomes receiver digitized subcarrier output

Direct TX modulation and

B5 MOD_Direct MOD pin becomes input for TX modulation control by the MCU

RX reset

o_sel = L: First stage output used for analog out and digitizing

B4 o_sel First stage output selection o_sel = H: Second Stage output used for analog out and digitizing

Second stage gain -6 dB,

B3 low2 HP corner frequency/2

First stage gain -6 dB, HP

B2 low1 corner frequency/2

B1 zun Input followers test

AGC test, AGC level is

B0 Test_AGC seen on rssi_210 bits

6.14.3.4.2 Test Register 0x1B

Table 6-55. Test Register (0x1B) (for Test or Direct Use)

Default: 0x00 at POR = H and EN = L. When a test_dec or test_io is set IC is switched to test mode. Test Mode persists until a stop

condition arrives. At stop condition the test_dec and test_io bits are cleared.

Bit Name Function Description

B6 test_rf_level RF level test

B3 test_io1 I/O test Not implemented

B2 test_io0

B1 test_dec Decoder test mode

B0 clock_su Coder clock 13.56 MHz For faster test of coders

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6.14.3.5 FIFO Control Registers

6.14.3.5.1 FIFO Status Register (0x1C)

Table 6-56. FIFO Status Register (0x1C)

Function: Number of bytes available to be read from FIFO (= N number of bytes, in hexadecimal)

Bit Name Function Description

B7 Foverflow FIFO overflow error Bit is set when FIFO has more than 127 bytes presented to it

B6 Fb6 FIFO bytes fb[6]

B5 Fb5 FIFO bytes fb[5]

B4 Fb4 FIFO bytes fb[4]

B3 Fb3 FIFO bytes fb[3]

B2 Fb2 FIFO bytes fb[2] Bits B0:B6 indicate how many bytes that are in the FIFO to be read out (= N

number of bytes, in hex)

B1 Fb1 FIFO bytes fb[1]

B0 Fb0 FIFO bytes fb[0]

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6.14.3.5.2 TX Length Byte1 Register (0x1D), TX Length Byte2 Register (0x1E)

Table 6-57. TX Length Byte1 Register (0x1D)

Function: High 2 nibbles of complete, intended bytes to be transferred through FIFO

Bit Name Function Description

Number of complete byte

B7 Txl11 bn[11]

Number of complete byte

B6 Txl10 bn[10] High nibble of complete, intended bytes to be transmitted

Number of complete byte

B5 Txl9 bn[9]

Number of complete byte

B4 Txl8 bn[8]

Number of complete byte

B3 Txl7 bn[7]

Number of complete byte

B2 Txl6 bn[6] Middle nibble of complete, intended bytes to be transmitted

Number of complete byte

B1 Txl5 bn[5]

Number of complete byte

B0 Txl4 bn[4]

Table 6-58. TX Length Byte2 Register (0x1E)

Function: Low nibbles of complete bytes to be transferred through FIFO; Information about a broken byte and number of bits to be

transferred from it

Default: 0x00 at POR and EN = 0. It is also automatically reset at TX EOF

Bit Name Function Description

Number of complete byte

B7 Txl3 bn[3]

Number of complete byte

B6 Txl2 bn[2] Low nibble of complete, intended bytes to be transmitted

Number of complete byte

B5 Txl1 bn[1]

Number of complete byte

B4 Txl0 bn[0]

Broken byte number of bits

B3 Bb2 bb[2]

Broken byte number of bits Number of bits in the last broken byte to be transmitted.

B2 Bb1 bb[1] It is taken into account only when broken byte flag is set.

Broken byte number of bits

B1 Bb0 bb[0]

B0 Bbf Broken byte flag B0 = 1, indicates that last byte is not complete 8 bits wide.

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7 Application Schematic and Layout Considerations

7.1 TRF7970A Reader System Using Parallel Microcontroller Interface

7.1.1 General Application Considerations

Figure 7-1 shows the most flexible TRF7970A application schematic. Both ISO15693, ISO14443 and

FeliCa systems can be addressed. Due to the low clock frequency on the DATA_CLK line, the parallel

interface is the most robust way to connect the TRF7970A with the MCU.

Figure 7-1 shows matching to a 50-Ωport, which allows connecting to a properly matched 50-Ωantenna

circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).

An MSP430F2370 (32KB Flash, 2KB RAM) is shown in Figure 7-1. Minimum MCU requirements depend

on application requirements and coding style. If only one ISO protocol or a limited command set of a

protocol needs to be supported, MCU Flash and RAM requirements can be significantly reduced. Be

aware that recursive inventory and anticollision commands require more RAM than single slotted

operations. For example, current reference firmware for ISO15693 (with host interface) is approximately

8KB, using 512B RAM; for all supported protocols (also with same host interface) the reference firmware

is approximately 12KB and uses a minimum of 1KB RAM. An MCU capable of running its GPIOs at

13.56 MHz is required for Direct Mode 0 operations.

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7.2 TRF7970A Reader System Using SPI With SS Mode

7.2.1 General Application Considerations

Figure 7-2 shows the TRF7970A application schematic optimized for both ISO15693 and ISO14443

systems using the Serial Port Interface (SPI). Short SPI lines, proper isolation of radio frequency lines,

and a proper ground area are essential to avoid interference. The recommended clock frequency on the

DATA_CLK line is 2 MHz.

Figure 7-2 shows matching to a 50-Ωport, which allows connecting to a properly matched 50-Ωantenna

circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).

An MSP430F2370 (32KB Flash, 2KB RAM) is shown in Figure 7-2. Minimum MCU requirements depend

on application requirements and coding style. If only one ISO protocol or a limited command set of a

protocol needs to be supported, MCU Flash and RAM requirements can be significantly reduced and user

should be aware that recursive inventory and anticollision commands require more RAM than single

slotted operations. For example, current reference firmware for ISO15693 (with host interface) is

approximately 8KB, using 512B RAM and for all supported protocols (also with same host interface) the

reference firmware is approximately 12KB and uses a minimum of 1KB RAM. An MCU capable of running

its GPIOs at 13.56 MHz is required for Direct Mode 0 operations.

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7.3 Layout Considerations

Keep all decoupling capacitors as close to the IC as possible, with the high-frequency decoupling

capacitors (10 nF) closer than the low-frequency decoupling capacitors (2.2 µF).

Place ground vias as close as possible to the ground side of the capacitors and reader IC pins to minimize

possible ground loops.

It is not recommend to use any inductor sizes below 0603, as the output power can be compromised. If

smaller inductors are necessary, output performance must be confirmed in the final application.

Pay close attention to the required load capacitance of the crystal, and adjust the two external shunt

capacitors accordingly. Follow the recommendations of the crystal manufacturer for those values.

There should be a common ground plane for the digital and analog sections. The multiple ground sections

or islands should have vias that tie the different sections of the planes together.

Ensure that the exposed thermal pad at the center of the reader IC is properly laid out. It should be tied to

ground to help dissipate any heat from the package.

All trace line lengths should be made as short as possible, particularly the RF output path, crystal

connections, and control lines from the reader to the microprocessor. Proper placement of the TRF7970A,

microprocessor, crystal, and RF connection or connector help facilitate this.

Avoid crossing of digital lines under RF signal lines. Also, avoid crossing of digital lines with other digital

lines when possible. If the crossings are unavoidable, 90° crossings should be used to minimize coupling

of the lines.

Depending on the production test plan, consider possible implementations of test pads or test vias for use

during testing. The necessary pads or vias should be placed in accordance with the proposed test plan to

enable easy access to those test points.

If the system implementation is complex (for example, if the RFID reader module is a subsystem of a

greater system with other modules (Bluetooth, WiFi, microprocessors, and clocks), special considerations

should be taken to ensure that there is no noise coupling into the supply lines. If needed, special filtering

or regulator considerations should be used to minimize or eliminate noise in these systems.

For more information/details on layout considerations, see the TRF796x HF-RFID Reader Layout Design

Guide (SLOA139).

7.4 Impedance Matching TX_Out (Pin 5) to 50 Ω

The output impedance of the TRF7970A when operated at full power out setting is nominally 4 + j0 (4 Ω

real). This impedance must be matched to a resonant circuit and TI recommends matching circuit from

4Ωto 50 Ω, as commercially available test equipment (for example, spectrum analyzers, power meters,

and network analyzers) are 50-Ωsystems. An impedance-matching reference circuit can be seen in

Figure 7-3 and Figure 7-4. This section explains how the values were calculated.

Starting with the 4-Ωsource, the process of going from 4 Ωto 50 Ωcan be represented on a Smith Chart

simulator (available from http://www.fritz.dellsperger.net/). The elements are combined where appropriate

(see Figure 7-3).

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Figure 7-3. Impedance Matching Circuit

This yields the Smith Chart Simulation shown in Figure 7-4.

Figure 7-4. Smith Chart Simulation

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Resulting power out can be measured with a power meter or spectrum analyzer with power meter function

or other equipment capable of making a "hot" measurement. Observe maximum power input levels on test

equipment and use attenuators whenever available to avoid damage to equipment. Expected output

power levels under various operating conditions are shown in Table 6-25.

7.5 Reader Antenna Design Guidelines

For HF antenna design considerations using the TRF7970A, see these documents:

•Antenna Matching for the TRF7960 RFID Reader (SLOA135)

•TRF7960TB HF RFID Reader Module User's Guide (SLOU297)

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8 Device and Documentation Support

8.1 Documentation Support

The following documents describe the TRF7970A device. Copies of these documents are available on the

Internet at www.ti.com.

SLOZ011 TRF7970A Silicon Errata. Describes the known exceptions to the functional specifications

for the TRF7970A.

8.2 Community Resources

The following links connect to TI community resources. Linked contents are provided "AS IS" by the

respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views;

see TI's Terms of Use.

TI E2E Community

TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At

e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow

engineers.

8.3 Trademarks

MSP430 is a trademark of Texas Instruments.

ARM is a registered trademark of ARM Limited.

Bluetooth is a registered trademark of Bluetooth SIG.

MIFARE is a trademark of NXP Semiconductors.

FeliCa is a trademark of Sony Corporation.

Wi-Fi is a registered trademark of Wi-Fi Alliance.

All other trademarks are the property of their respective owners.

8.4 Electrostatic Discharge Caution

This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with

appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.

ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more

susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.

8.5 Glossary

SLYZ022 —TI Glossary.

This glossary lists and explains terms, acronyms and definitions.

9 Mechanical Packaging and Orderable Information

9.1 Packaging Information

The following pages include mechanical packaging and orderable information. This information is the most

current data available for the designated devices. This data is subject to change without notice and

revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation.

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Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

TRF7970ARHBR ACTIVE VQFN RHB 32 3000 Green (RoHS

& no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR TRF

7970A

TRF7970ARHBT ACTIVE VQFN RHB 32 250 Green (RoHS

& no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR TRF

7970A

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability

information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that

lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between

the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight

in homogeneous material)

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

PACKAGE OPTION ADDENDUM

www.ti.com 4-Apr-2014

Addendum-Page 2

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

TRF7970ARHBR VQFN RHB 32 3000 330.0 12.4 5.3 5.3 1.5 8.0 12.0 Q2

TRF7970ARHBT VQFN RHB 32 250 180.0 12.4 5.3 5.3 1.5 8.0 12.0 Q2

PACKAGE MATERIALS INFORMATION

www.ti.com 15-Jan-2015

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

TRF7970ARHBR VQFN RHB 32 3000 367.0 367.0 35.0

TRF7970ARHBT VQFN RHB 32 250 210.0 185.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 15-Jan-2015

Pack Materials-Page 2

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