PIC32MX FRM Section 31. DMA Controller PIC32 Family Reference Manual, Sect. 31

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31
DMA Controller

Section 31. DMA Controller
HIGHLIGHTS
This section of the manual contains the following major topics:
31.1
31.2
31.3
31.4
31.5
31.6
31.7
31.8

© 2010 Microchip Technology Inc.

Introduction.............................................................................................................. 31-2
Status and Control Registers ................................................................................... 31-5
Modes of Operation ............................................................................................... 31-31
Interrupts................................................................................................................ 31-51
Operation in Power-Saving and Debug Modes ..................................................... 31-55
Effects of Various Resets....................................................................................... 31-55
Related Application Notes ..................................................................................... 31-56
Revision History..................................................................................................... 31-57

DS61117F-page 31-1

PIC32MX Family Reference Manual
Note:

This family reference manual section is meant to serve as a complement to device
data sheets. Depending on the device variant, this manual section may not apply to
all PIC32MX devices.
Please consult the note at the beginning of the “Direct Memory Access (DMA)
Controller” chapter in the current device data sheet to check whether this
document supports the device you are using.
Device data sheets and family reference manual sections are available for
download from the Microchip Worldwide Web site at: http://www.microchip.com

31.1

INTRODUCTION
The Direct Memory Access (DMA) controller is a bus master module that is useful for data transfers between different peripherals without intervention from the CPU. The source and destination
of a DMA transfer can be any of the memory-mapped modules included in the PIC32MX. For
example, memory, or one of the Peripheral Bus (PBUS) devices such as SPI, UART and so on.
Following are some of the key features of the DMA module:
• Depending on the device variant, up to eight identical channels are available, including the
following:
- Auto-Increment Source and Destination Address registers
- Source and Destination Pointers
• Depending on the device variant, data transfers of up to 64 Kbytes are supported
• Automatic Word-Size Detection, featuring the following:
- Transfer granularity down to byte level
- Bytes need not be word-aligned at source and destination
• Fixed Priority Channel Arbitration
• Flexible DMA Channel Operating modes, including the following:
- Manual (software) or automatic (interrupt) DMA requests
- One-Shot or Auto-Repeat Block Transfer modes
- Channel-to-channel chaining
• Flexible DMA Requests, featuring the following:
- A DMA request can be selected from any of the peripheral interrupt sources
- Each channel can select any interrupt as its DMA request source
- A DMA transfer abort can be selected from any of the peripheral interrupt sources
- Automatic transfer termination upon a data pattern match
• Multiple DMA Channel Status Interrupts, supplying the following:
- DMA channel block transfer complete
- Source empty or half empty
- Destination full or half full
- DMA transfer aborted due to an external event
- Invalid DMA address generated
• DMA Debug Support Features, including the following:
- Most recent address accessed by a DMA channel
- Most recent DMA channel to transfer data
• CRC Generation Module, featuring the following:
- CRC module can be assigned to any of the available channels
- Data read from the source can be reordered on some device variants
- CRC module is highly configurable
The following features are also available in the DMA controller:
•
•
•
•
•
•
•
•
•

DS61117F-page 31-2

Unaligned Transfers
Different Source and Destination Sizes
Memory-to-Memory Transfers
Memory-to-Peripheral Transfers
Channel Auto-Enable
Events Start/Stop
Pattern Match Detection
Channel Chaining
CRC Calculation

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
DMA Operation

A DMA channel transfers data from a source to a destination without CPU intervention. The
source and destination start addresses define the start address of the source and destination,
respectively.
Both the source and destination have independently configurable sizes and the number of the
transferred bytes is independent of the source and destination sizes.
A transfer is initiated either by software or by an interrupt request. The user can select any
interrupt on the device to start a DMA transfer.
Upon transfer initiation, the DMA controller will perform a cell transfer and the channel remains
enabled until a block transfer is complete. When a channel is disabled, further transfers will be
prohibited until the channel is re-enabled.
The DMA channel uses separate pointers to keep track of the current word locations at the
source and destination.
Interrupts can be generated when the source/destination pointer is half of the source/destination
size, or when the source/destination counter reaches the end of the source/destination.
A DMA transfer can be aborted by the software, by a pattern match or by an interrupt event. The
transfer will also stop when an address error is detected.
Figure 31-1:

Typical DMA Source to Destination Transfer Diagram

[Source Device/Memory]

[Destination Device/Memory]

1/2/3/4 Bytes in Access Size

1/2/3/4 Bytes in Access Size

Start Transfer

Stop Transfer

IRQ

IRQ

DMA

Software Start Transfer

© 2010 Microchip Technology Inc.

Software Abort Transfer

DS61117F-page 31-3

DMA Controller

31.1.1

31

PIC32MX Family Reference Manual
Figure 31-2:

DMA Module Block Diagram

INT Controller

System IRQ

Peripheral Bus

Address Decoder

SE
L

Channel 0 Control

I0

Channel 1 Control

I1

Bus Interface

Y

Device Bus + Bus Arbitration

I2

Global Control
(DMACON)

Channel n Control

In
L
SE

Channel Priority
Arbitration

Figure 31-3:

CRC Implementation Details
CRC Seed Write

CRC Data Read
DataIn

Q

SET

Q

D

SET

D

Q

SET

D

<

<

Q CLR
Stage 30

Q CLR
Stage 31(1)

Q

SET

<
Q CLR
Stage 29

D

Q

SET

<
Q CLR
Stage 1

D

<
Q CLR
Stage 0

Clk

Stage Feedback
enable

Note 1:

Stage Feedback
enable

Stage Feedback
enable

Depending on the device variant, up to 32 stages (0 through 31) are available. Refer to the specific
device data sheet for more details.

DS61117F-page 31-4

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
STATUS AND CONTROL REGISTERS
Note:

Each PIC32MX device variant may have one or more DMA channels. An ‘x’ used in
the names of Control/Status bits and registers denotes the particular channel. Refer
to the specific device data sheets for more details.

The DMA module consists of the following Special Function Registers (SFRs):
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

DMACON: DMA Controller Control Register(1,2,3)
DMASTAT: DMA Status Register(1)
DMAADDR: DMA Address Register(1)
DCRCCON: DMA CRC Control Register(1,2,3)
DCRCDATA: DMA CRC Data Register(1,2,3) – The initial value of the CRC generator
DCRCXOR: DMA CRCXOR Enable Register(1,2,3) – Provides a description of the generator polynomial for CRC calculation
DCHxCON: DMA Channel x Control Register(1,2,3)
DCHxECON: DMA Channel x Event Control Register(1,2,3)
DCHxINT: DMA Channel x Interrupt Control Register(1,2,3)
DCHxSSA: DMA Channel x Source Start Address Register(1,2,3)
DCHxDSA: DMA Channel x Destination Start Address Register
DCHxSSIZ: DMA Channel x Source Size Register(1,2,3)
DCHxDSIZ: DMA Channel x Destination Size Register(1,2,3)
DCHxSPTR: DMA Channel x Source Pointer Register(1)
DCHxDPTR: DMA Channel x Destination Pointer Register
DCHxCSIZ: DMA Channel x Cell-Size Register(1,2,3)
DCHxCPTR: DMA Channel x Cell Pointer Register(1)
DCHxDAT: DMA Channel x Pattern Data Register(1,2,3)

Table 31-1 provides a brief summary of DMA-module-related registers. Corresponding registers
appear after the summary, followed by a detailed description of each register.

© 2010 Microchip Technology Inc.

DS61117F-page 31-5

DMA Controller

31.2

31

PIC32MX Family Reference Manual
Table 31-1:
Address
Offset

DMA Register Summary
Bit
Range

Name
DMACON(1,2,3)

0x00

0x10

DMASTAT

0x20

DMAADDR

Bit
31/23/15/7

Bit
30/22/14/6

Bit
29/21/13/5

Bit
28/20/12/4

Bit
27/19/11/3

Bit
26/18/10/2

Bit
25/17/9/1

Bit
24/16/8/0

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

ON

FRZ

SIDL(4)

SUSPEND

DMABUSY(4)

—

—

—

7:0

—

—

—

—

—

—

—

—

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

—

—

—

—

—

—

—

—

7:0

—

—

—

—

RDWR

31:24

DMAADDR<31:24>

23:16

DMAADDR<23:16>

15:8

DMAADDR<15:8>

7:0
(1,2,3)

0x30

DCRCCON

(1,2,3)

0x40

DCRCDATA

DCRCXOR(1,2,3)

0x50

(1,2,3)

0x60

DCHxCON

DMAADDR<7:0>
—

—

23:16

—

—

—

15:8

—

—

—

7:0

CRCEN

CRCAPP

CRCTYP(4)

DCHxECON

DCHxSSA(1,2,3)

0x90

Legend:
Note 1:
2:
3:
4:
5:

—

—

—

BITO(4)

—

—

—

PLEN<4:0>(5)
—

CRCCH<2:0>(5)

—
(5)

DCRCDATA<23:16>(5)

15:8

DCRCDATA<15:8>(5)

7:0

DCRCDATA<7:0>(5)

31:24

DCRCXOR<31:24>(5)

23:16

DCRCXOR<23:16>(5)

15:8

DCRCXOR<15:8>(5)

7:0

DCRCXOR<7:0>(5)

31:24

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

—

—

—

—

—

—

CHCHNS

CHEN

CHAED

CHCHN

CHAEN

—

CHEDET

—

—

—

—

—

—

—

—

—

—

—

31:24

7:0
DCHxINT

—

DCRCDATA<31:24>

—

CHPRI<1:0>

CHAIRQ<7:0>
CHSIRQ<7:0>

15:8

0x80

WBO(4)

23:16

23:16

(1,2,3)

BYTO0(4)

31:24

7:0
0x70

BYTO1

(4)

31:24

15:8 CHBUSY(4)
(1,2,3)

DMACH<2:0>(5)

CFORCE

CABORT

PATEN

SIRQEN

AIRQEN

31:24

—

—

—

—

—

—

—

—

23:16

CHSDIE

CHSHIE

CHDDIE

CHDHIE

CHBCIE

CHCCIE

CHTAIE

CHERIE

15:8

—

—

—

—

—

—

—

—

7:0

CHSDIF

CHSHIF

CHDDIF

CHDHIF

CHBCIF

CHCCIF

CHTAIF

CHERIF

31:24

CHSSA<31:24>

23:16

CHSSA<23:16>

15:8

CHSSA<15:8>

7:0

CHSSA<7:0>

— = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.
This register has an associated Clear register at an offset of 0x4 bytes. These registers have the same name with CLR appended to the end
of the register name (e.g., DMACONCLR). Writing a ‘1’ to any bit position in the Clear register will clear valid bits in the associated register.
Reads from the Clear register should be ignored.
This register has an associated Set register at an offset of 0x8 bytes. These registers have the same name with SET appended to the end
of the register name (e.g., DMACONSET). Writing a ‘1’ to any bit position in the Set register will set valid bits in the associated register.
Reads from the Set register should be ignored.
This register has an associated Invert register at an offset of 0xC bytes. These registers have the same name with INV appended to the end
of the register name (e.g., DMACONINV). Writing a ‘1’ to any bit position in the Invert register will invert valid bits in the associated register.
Reads from the Invert register should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more details.

DS61117F-page 31-6

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

Address
Offset
0xA0

DMA Register Summary (Continued)
Name

DCHxDSA

Bit
Range

Bit
31/23/15/7

Bit
30/22/14/6

Bit
29/21/13/5

DCHxDSIZ(1,2,3)

0xC0

0xD0

DCHxSPTR

0xE0

DCHxDPTR

DCHxCSIZ(1,2,3)

0xF0

0x100

DCHxCPTR

(1,2,3)

0x110

DCHxDAT

31:24

CHDSA<31:24>
CHDSA<23:16>

15:8

CHDSA<15:8>

2:
3:
4:
5:

Bit
26/18/10/2

Bit
25/17/9/1

Bit
24/16/8/0

CHDSA<7:0>

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHSSIZ<15:8>(5)

7:0

CHSSIZ<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHDSIZ<15:8>(5)

7:0

CHDSIZ<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHSPTR<15:8>(5)

7:0

CHSPTR<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHDPTR<15:8>(5)

7:0

CHDPTR<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHCSIZ<15:8>(5)

7:0

CHCSIZ<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

CHCPTR<15:8>(5)

7:0

CHCPTR<7:0>(5)

31:24

—

—

—

—

—

—

—

—

23:16

—

—

—

—

—

—

—

—

15:8

—

—

—

—

—

—

—

—

7:0
Legend:
Note 1:

Bit
27/19/11/3

23:16

7:0
DCHxSSIZ(1,2,3)

0xB0

Bit
28/20/12/4

CHPDAT<7:0>

— = unimplemented, read as ‘0’. Address offset values are shown in hexadecimal.
This register has an associated Clear register at an offset of 0x4 bytes. These registers have the same name with CLR appended to the end
of the register name (e.g., DMACONCLR). Writing a ‘1’ to any bit position in the Clear register will clear valid bits in the associated register.
Reads from the Clear register should be ignored.
This register has an associated Set register at an offset of 0x8 bytes. These registers have the same name with SET appended to the end
of the register name (e.g., DMACONSET). Writing a ‘1’ to any bit position in the Set register will set valid bits in the associated register.
Reads from the Set register should be ignored.
This register has an associated Invert register at an offset of 0xC bytes. These registers have the same name with INV appended to the end
of the register name (e.g., DMACONINV). Writing a ‘1’ to any bit position in the Invert register will invert valid bits in the associated register.
Reads from the Invert register should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-7

DMA Controller

Table 31-1:

31

PIC32MX Family Reference Manual
DMACON: DMA Controller Control Register(1,2,3)
U-0
U-0
U-0
U-0

Register 31-1:
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

U-0

U-0

U-0

ON

FRZ

SIDL(4)

SUSPEND

DMABUSY(4)

—

—

—

bit 15

bit 8

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15

ON: DMA On bit
1 = DMA module is enabled
0 = DMA module is disabled
Note:

P = Programmable bit

r = Reserved bit

When using 1:1 PBCLK divisor, the user’s software should not read/write the peripheral’s
SFRs in the SYSCLK cycle immediately following the instruction that clears the module’s
ON bit.

bit 14

FRZ: DMA Freeze bit
1 = DMA is frozen during Debug mode
0 = DMA continues to run during Debug mode

bit 13

SIDL: Stop in Idle Mode bit(4)
1 = DMA transfers are frozen during Idle
0 = DMA transfers continue during Idle

bit 12

SUSPEND: DMA Suspend bit
1 = DMA transfers are suspended to allow CPU uninterrupted access to data bus
0 = DMA operates normally

Note:

Note 1:

2:

3:

4:

FRZ is writable in Debug Exception mode only, it is forced to ‘0’ in Normal mode.

This register has an associated Clear register (DMACONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to any
bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear register
should be ignored.
This register has an associated Set register (DMACONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DMACONINV) at an offset of 0xC bytes. Writing a ‘1’ to any bit
position in the Invert register will invert valid bits in the associated register. Reads from the Invert register
should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.

DS61117F-page 31-8

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Register 31-1: DMACON: DMA Controller Control
(Continued)
bit 11
DMABUSY: DMA Module Busy bit(4)
1 = DMA module is active
0 = DMA module is disabled and not actively transferring data
bit 10-0
Note 1:

2:

3:

4:

Unimplemented: Read as ‘0’
This register has an associated Clear register (DMACONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to any
bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear register
should be ignored.
This register has an associated Set register (DMACONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DMACONINV) at an offset of 0xC bytes. Writing a ‘1’ to any bit
position in the Invert register will invert valid bits in the associated register. Reads from the Invert register
should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-9

31
DMA Controller

Register(1,2,3)

PIC32MX Family Reference Manual
DMASTAT: DMA Status Register(1)
U-0
U-0
U-0

Register 31-2:
U-0
—

—

—

—

U-0

U-0

U-0

U-0

—

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 15

bit 8

U-0

U-0

U-0

U-0

R-0

—

—

—

—

RDWR

R-0

R-0

R-0

DMACH<2:0>(2)

bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-4

Unimplemented: Read as ‘0’

bit 3

RDWR: Read/Write Status bit
1 = Last DMA bus access was a read
0 = Last DMA bus access was a write

bit 2-0

DMACH<2:0>: DMA Channel bits(2)

Note 1:
2:

P = Programmable bit

r = Reserved bit

This register contains the value of the most recent active DMA channel.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

DS61117F-page 31-10

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

R-0

R-0

R-0

R-0

DMAADDR<31:24>
bit 31

bit 24

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

DMAADDR<23:16>
bit 23

bit 16

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

DMAADDR<15:8>
bit 15

bit 8

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

DMAADDR<7:0>
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-0
Note 1:

P = Programmable bit

r = Reserved bit

DMAADDR<31:0>: DMA Module Address bits
This register contains the address of the most recent DMA access.

© 2010 Microchip Technology Inc.

DS61117F-page 31-11

DMA Controller

DMAADDR: DMA Address Register(1)
R-0
R-0
R-0

Register 31-3:
R-0

31

PIC32MX Family Reference Manual
DCRCCON: DMA CRC Control Register(1,2,3)
U-0
R/W-0
R/W-0
R/W-0

Register 31-4:
U-0
—

—

BYTO<1:0>(4)

WBO(4,5)

U-0

U-0

R/W-0

—

—

BITO(4)

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

U-0

U-0

U-0

—

—

—

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

PLEN<4:0>(5)

bit 15

bit 8

R/W-0

R/W-0

R/W-0

U-0

U-0

CRCEN

CRCAPP(5)

CRCTYP(4)

—

—

R/W-0

R/W-0

R/W-0

CRCCH<2:0>(4)

bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

r = Reserved bit

bit 31-30

Unimplemented: Read as ‘0’

bit 29-28

BYTO<1:0>: CRC Byte Order Selection bits(4)
11 = Endian byte swap on half-word boundaries (i.e., source half-word order with reverse source byte
order per half-word)
10 = Swap half-words on word boundaries (i.e., reverse source half-word order with source byte order
per half-word)
01 = Endian byte swap on word boundaries (i.e., reverse source byte order)
00 = No swapping (i.e., source byte order)

bit 27

WBO: CRC Write Byte Order Selection bit(4,5)
1 = Source data is written to the destination re-ordered as defined by BYTO<1:0>
0 = Source data is written to the destination unaltered

bit 26-25

Unimplemented: Read as ‘0’

Note 1:

2:

3:

4:
5:

This register has an associated Clear register (DCRCCONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCRCCONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCRCCONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available on all devices. Refer to the specific device data
sheet for more details.
When WBO = 1, unaligned transfers are not supported and the CRCAPP bit cannot be set.

DS61117F-page 31-12

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

31

(1,2,3)

When CRCTYP (DCRCCON<15>) = 0 (CRC module is in LFSR mode):
1 = The LFSR CRC is calculated Least Significant bit first (i.e., reflected)
0 = The LFSR CRC is calculated Most Significant bit first (i.e., not reflected)
bit 23-13

Unimplemented: Read as ‘0’

bit 12-8

PLEN<4:0>: Polynomial Length bits(5)
When CRCTYP (DCRCCON<15>) = 1 (CRC module is in IP Header mode):
These bits are unused.
When CRCTYP (DCRCCON<15>) = 0 (CRC module is in LFSR mode):
Denotes the length of the polynomial – 1.

bit 7

CRCEN: CRC Enable bit
1 = CRC module is enabled and channel transfers are routed through the CRC module
0 = CRC module is disabled and channel transfers proceed normally

bit 6

CRCAPP: CRC Append Mode bit(5)
1 = The DMA transfers data from the source into the CRC but NOT to the destination. When a block
transfer completes the DMA writes the calculated CRC value to the location given by CHxDSA
0 = The DMA transfers data from the source through the CRC obeying WBO as it writes the data to
the destination

bit 5

CRCTYP: CRC Type Selection bit(4)
1 = The CRC module will calculate an IP header checksum
0 = The CRC module will calculate a LFSR CRC

bit 4-3

Unimplemented: Read as ‘0’

bit 2-0

CRCCH<2:0>: CRC Channel Select bits(4)
111 = CRC is assigned to Channel 7
110 = CRC is assigned to Channel 6
101 = CRC is assigned to Channel 5
100 = CRC is assigned to Channel 4
011 = CRC is assigned to Channel 3
010 = CRC is assigned to Channel 2
001 = CRC is assigned to Channel 1
000 = CRC is assigned to Channel 0

Note 1:

2:

3:

4:
5:

This register has an associated Clear register (DCRCCONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCRCCONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCRCCONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available on all devices. Refer to the specific device data
sheet for more details.
When WBO = 1, unaligned transfers are not supported and the CRCAPP bit cannot be set.

© 2010 Microchip Technology Inc.

DS61117F-page 31-13

DMA Controller

(Continued)
Register 31-4: DCRCCON: DMA CRC Control Register
bit 24
BITO: CRC Bit Order Selection bit(4)
When CRCTYP (DCRCCON<15>) = 1 (CRC module is in IP Header mode):
1 = The IP header checksum is calculated Least Significant bit (LSb) first (i.e., reflected)
0 = The IP header checksum is calculated Most Significant bit (MSb) first (i.e., not reflected)

PIC32MX Family Reference Manual
DCRCDATA: DMA CRC Data Register(1,2,3)
R/W-0
R/W-0
R/W-0
R/W-0

Register 31-5:
R/W-0

R/W-0

R/W-0

R/W-0

DCRCDATA<31:24>(4)
bit 31

bit 24

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCDATA<23:16>(4)
bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCDATA<15:8>(4)
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCDATA<7:0>(4)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-0

P = Programmable bit

r = Reserved bit

DCRCDATA<31:0>: CRC Data Register bits(4)
Writing to this register will seed the CRC generator. Reading from this register will return the current
value of the CRC. Bits greater than PLEN will return ‘0’ on any read.
When CRCTYP (DCRCCON<15>) = 1 (CRC module is in IP Header mode):
Only the lower 16 bits contain IP header checksum information. The upper 16 bits are always ‘0’. Data
written to this register is converted and read back in 1’s complement form (i.e., current IP header
checksum value).
When CRCTYP (DCRCCON<15>) = 0 (CRC module is in LFSR mode):
Bits greater than PLEN will return ‘0’ on any read.

Note 1:

2:

3:

4:

This register has an associated Clear register (DCRCDATACLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCRCDATASET) at an offset of 0x8 bytes. Writing a ‘1’ to
any bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCRCDATAINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

DS61117F-page 31-14

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

R/W-0

R/W-0

R/W-0

DCRCXOR<31:24>(4)
bit 31

bit 24

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCXOR<23:16>(4)
bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCXOR<15:8>(4)
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

DCRCXOR<7:0>(4)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-0

P = Programmable bit

r = Reserved bit

DCRCXOR<31:0>: CRC XOR Register bits(4)
When CRCTYP (DCRCCON<15>) = 1 (CRC module is in IP Header mode):
This register is unused.
When CRCTYP (DCRCCON<15>) = 0 (CRC module is in LFSR mode):
1 = Enable the XOR input to the Shift register
0 = Disable the XOR input to the Shift register; data is shifted in directly from the previous stage in
the register

Note 1:

2:

3:

4:

This register has an associated Clear register (DCRCXORCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCRCXORSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCRCXORINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-15

DMA Controller

DCRCXOR: DMA CRCXOR Enable Register(1,2,3)
R/W-0
R/W-0
R/W-0
R/W-0

Register 31-6:
R/W-0

31

PIC32MX Family Reference Manual
DCHxCON: DMA Channel x Control Register(1,2,3)
U-0
U-0
U-0
U-0

Register 31-7:
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R/W-0

U-0

U-0

U-0

U-0

U-0

U-0

R/W-0

CHBUSY(4)

—

—

—

—

—

—

CHCHNS(5)

bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

U-0

R-0

CHEN(6)

CHAED

CHCHN

CHAEN

—

CHEDET

R/W-0

R/W-0

CHPRI<1:0>

bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

r = Reserved bit

bit 31-16

Unimplemented: Read as ‘0’

bit 15

CHBUSY: Channel Busy bit(4)
1 = Channel is active or has been enabled
0 = Channel is inactive or has been disabled

bit 14-9

Unimplemented: Read as ‘0’

bit 8

CHCHNS: Chain Channel Selection bit(5)
1 = Chain to channel lower in natural priority (CH1 will be enabled by CH2 transfer complete)
0 = Chain to channel higher in natural priority (CH1 will be enabled by CH0 transfer complete)

bit 7

CHEN: Channel Enable bit(6)
1 = Channel is enabled
0 = Channel is disabled

bit 6

CHAED: Channel Allow Events If Disabled bit
1 = Channel start/abort events will be registered, even if the channel is disabled
0 = Channel start/abort events will be ignored if the channel is disabled

Note 1:

2:

3:

4:
5:
6:

This register has an associated Clear register (DCHxCONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxCONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxCONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.
The chain selection bit takes effect when chaining is enabled (i.e., CHCHN = 1).
When the channel is suspended by clearing this bit, the user application should poll the CHBUSY bit (if
available on the device variant) to see when the channel is suspended, as it may take some clock cycles
to complete a current transaction before the channel is suspended.

DS61117F-page 31-16

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
(1,2,3)

(Continued)

bit 4

CHAEN: Channel Automatic Enable bit
1 = Channel is continuously enabled, and not automatically disabled after a block transfer is complete
0 = Channel is disabled on block transfer complete

bit 3

Unimplemented: Read as ‘0’

bit 2

CHEDET: Channel Event Detected bit
1 = An event has been detected
0 = No events have been detected

bit 1-0

CHPRI<1:0>: Channel Priority bits
11 = Channel has priority 3 (highest)
10 = Channel has priority 2
01 = Channel has priority 1
00 = Channel has priority 0

Note 1:

2:

3:

4:
5:
6:

This register has an associated Clear register (DCHxCONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxCONSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxCONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
This bit is not available on all devices. Refer to the specific device data sheet for more details.
The chain selection bit takes effect when chaining is enabled (i.e., CHCHN = 1).
When the channel is suspended by clearing this bit, the user application should poll the CHBUSY bit (if
available on the device variant) to see when the channel is suspended, as it may take some clock cycles
to complete a current transaction before the channel is suspended.

© 2010 Microchip Technology Inc.

DS61117F-page 31-17

DMA Controller

Register 31-7: DCHxCON: DMA Channel x Control Register
bit 5
CHCHN: Channel Chain Enable bit
1 = Allow channel to be chained
0 = Do not allow channel to be chained

31

PIC32MX Family Reference Manual
DCHxECON: DMA Channel x Event Control Register(1,2,3)
U-0
U-0
U-0
U-0
U-0
—
—
—
—
—

Register 31-8:
U-0
—
bit 31
R/W-1

R/W-1

R/W-1

R/W-1
R/W-1
CHAIRQ<7:0>

R/W-1

U-0
—

R/W-1

bit 23

U-0
—
bit 24
R/W-1
bit 16

R/W-1

R/W-1

R/W-1

R/W-1
R/W-1
CHSIRQ<7:0>

R/W-1

R/W-1

R/W-1

bit 15

bit 8

S-0
CFORCE
bit 7

S-0
CABORT

R/W-0
SIRQEN

R/W-0
AIRQEN

U-0
—

U-0
—

U-0
—
bit 0

Legend:
R = Readable bit
U = Unimplemented bit
bit 31-24
bit 23-16

R/W-0
PATEN

S = Settable bit
W = Writable bit
P = Programmable bit
-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

r = Reserved bit

Unimplemented: Read as ‘0’
CHAIRQ<7:0>: Channel Transfer Abort IRQ bits
11111111 = Interrupt 255 will abort any transfers in progress and set CHAIF flag
•
•
•

bit 15-8

00000001 = Interrupt 1 will abort any transfers in progress and set CHAIF flag
00000000 = Interrupt 0 will abort any transfers in progress and set CHAIF flag
CHSIRQ<7:0>: Channel Transfer Start IRQ bits
11111111 = Interrupt 255 will initiate a DMA transfer
•
•
•

00000001 = Interrupt 1 will initiate a DMA transfer
00000000 = Interrupt 0 will initiate a DMA transfer
CFORCE: DMA Forced Transfer bit
1 = A DMA transfer is forced to begin when this bit is written to a ‘1’
0 = This bit always reads ‘0’
CABORT: DMA Abort Transfer bit
1 = A DMA transfer is aborted when this bit is written to a ‘1’
0 = This bit always reads ‘0’

bit 7

bit 6

Note 1:

2:

3:

This register has an associated Clear register (DCHxECONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxECONSET) at an offset of 0x8 bytes. Writing a ‘1’ to
any bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxECONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.

DS61117F-page 31-18

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

31

(1,2,3)

Note 1:

2:

3:

DMA Controller

(Continued)
Register 31-8: DCHxECON: DMA Channel x Event Control Register
bit 5
PATEN: Channel Pattern Match Abort Enable bit
1 = Abort transfer and clear CHEN on pattern match
0 = Pattern match is disabled
bit 4
SIRQEN: Channel Start IRQ Enable bit
1 = Start channel cell transfer if an interrupt matching CHSIRQ occurs
0 = Interrupt number CHSIRQ is ignored and does not start a transfer
bit 3
AIRQEN: Channel Abort IRQ Enable bit
1 = Channel transfer is aborted if an interrupt matching CHAIRQ occurs
0 = Interrupt number CHAIRQ is ignored and does not terminate a transfer
bit 2-0
Unimplemented: Read as ‘0’
This register has an associated Clear register (DCHxECONCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxECONSET) at an offset of 0x8 bytes. Writing a ‘1’ to
any bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxECONINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.

© 2010 Microchip Technology Inc.

DS61117F-page 31-19

PIC32MX Family Reference Manual
DCHxINT: DMA Channel x Interrupt Control Register(1,2,3)
U-0
U-0
U-0
U-0
U-0

Register 31-9:
U-0
—

—

—

—

—

—

U-0

U-0

—

—

bit 31

bit 24

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSDIE

CHSHIE

CHDDIE

CHDHIE

CHBCIE

CHCCIE

CHTAIE

CHERIE

bit 23

bit 16

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSDIF

CHSHIF

CHDDIF

CHDHIF

CHBCIF

CHCCIF

CHTAIF

CHERIF

bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-24

Unimplemented: Read as ‘0’

bit 23

CHSDIE: Channel Source Done Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 22

CHSHIE: Channel Source Half Empty Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 21

CHDDIE: Channel Destination Done Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 20

CHDHIE: Channel Destination Half Full Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 19

CHBCIE: Channel Block Transfer Complete Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 18

CHCCIE: Channel Cell Transfer Complete Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

Note 1:

2:

3:

r = Reserved bit

This register has an associated Clear register (DCHxINTCLR) at an offset of 0x4 bytes. Writing a ‘1’ to any
bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear register
should be ignored.
This register has an associated Set register (DCHxINTSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxINTINV) at an offset of 0xC bytes. Writing a ‘1’ to any
bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert register
should be ignored.

DS61117F-page 31-20

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
(1,2,3)

(Continued)

DMA Controller

Register 31-9: DCHxINT: DMA Channel x Interrupt Control Register
bit 17
CHTAIE: Channel Transfer Abort Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled
bit 16

CHERIE: Channel Address Error Interrupt Enable bit
1 = Interrupt is enabled
0 = Interrupt is disabled

bit 15-8

Unimplemented: Read as ‘0’

bit 7

CHSDIF: Channel Source Done Interrupt Flag bit
1 = Channel Source Pointer has reached end of source (CHSPTR = CHSSIZ)
0 = No interrupt is pending

bit 6

CHSHIF: Channel Source Half Empty Interrupt Flag bit
1 = Channel Source Pointer has reached midpoint of source (CHSPTR = CHSSIZ/2)
0 = No interrupt is pending

bit 5

CHDDIF: Channel Destination Done Interrupt Flag bit
1 = Channel Destination Pointer has reached end of destination (CHDPTR = CHDSIZ)
0 = No interrupt is pending

bit 4

CHDHIF: Channel Destination Half Full Interrupt Flag bit
1 = Channel Destination Pointer has reached midpoint of destination (CHDPTR = CHDSIZ/2)
0 = No interrupt is pending

bit 3

CHBCIF: Channel Block Transfer Complete Interrupt Flag bit
1 = A block transfer has been completed (the larger of CHSSIZ/CHDSIZ bytes has been transferred),
or a pattern match event occurs
0 = No interrupt is pending

bit 2

CHCCIF: Channel Cell Transfer Complete Interrupt Flag bit
1 = A cell transfer has been completed (CHCSIZ bytes have been transferred)
0 = No interrupt is pending

bit 1

CHTAIF: Channel Transfer Abort Interrupt Flag bit
1 = An interrupt matching CHAIRQ has been detected and the DMA transfer has been aborted
0 = No interrupt is pending

bit 0

CHERIF: Channel Address Error Interrupt Flag bit
1 = A channel address error has been detected
Either the source or the destination address is invalid.
0 = No interrupt is pending

Note 1:

2:

3:

This register has an associated Clear register (DCHxINTCLR) at an offset of 0x4 bytes. Writing a ‘1’ to any
bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear register
should be ignored.
This register has an associated Set register (DCHxINTSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxINTINV) at an offset of 0xC bytes. Writing a ‘1’ to any
bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert register
should be ignored.

© 2010 Microchip Technology Inc.

31

DS61117F-page 31-21

PIC32MX Family Reference Manual
Register 31-10: DCHxSSA: DMA Channel x Source Start Address Register(1,2,3)
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0

R/W-0

R/W-0

CHSSA<31:24>
bit 31

bit 24

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSSA<23:16>
bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSSA<15:8>
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSSA<7:0>
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-0

P = Programmable bit

r = Reserved bit

CHSSA<31:0> Channel Source Start Address bits
Channel source start address.
Note: This must be the physical address of the source.

Note 1:

2:

3:

This register has an associated Clear register (DCHxSSACLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxSSASET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxSSAINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.

DS61117F-page 31-22

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

R/W-0

R/W-0

CHDSA<31:24>
bit 31

bit 24

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHDSA<23:16>
bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHDSA<15:8>
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHDSA<7:0>
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-0

P = Programmable bit

r = Reserved bit

CHDSA<31:0>: Channel Destination Start Address bits
Channel destination start address.
Note: This must be the physical address of the destination.

© 2010 Microchip Technology Inc.

DS61117F-page 31-23

DMA Controller

Register 31-11: DCHxDSA: DMA Channel x Destination Start Address Register
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0

31

PIC32MX Family Reference Manual
Register 31-12: DCHxSSIZ: DMA Channel x Source Size Register(1,2,3)
U-0
U-0
U-0
U-0
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSSIZ<15:8>(4)
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHSSIZ<7:0>(4)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHSSIZ<15:0>: Channel Source Size bits(4)
1111111111111111 = 65,535 byte source size
•
•
•
0000000000000010 = 2 byte source size
0000000000000001 = 1 byte source size
0000000000000000 = 65,536 byte source size

Note 1:

2:

3:

4:

r = Reserved bit

This register has an associated Clear register (DCHxSSIZCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxSSIZSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxSSIZINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

DS61117F-page 31-24

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

—

—

—

—

—

—

U-0

U-0

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHDSIZ<15:8>(4)
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHDSIZ<7:0>(4)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHDSIZ<15:0>: Channel Destination Size bits(4)
1111111111111111 = 65,535 byte destination size
•
•
•
0000000000000010 = 2 byte destination size
0000000000000001 = 1 byte destination size
0000000000000000 = 65,536 byte destination size

Note 1:

2:

3:

4:

r = Reserved bit

This register has an associated Clear register (DCHxDSIZCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxDSIZSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxDSIZINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-25

DMA Controller

Register 31-13: DCHxDSIZ: DMA Channel x Destination Size Register(1,2,3)
U-0
U-0
U-0
U-0
U-0
U-0

31

PIC32MX Family Reference Manual
Register 31-14: DCHxSPTR: DMA Channel x Source Pointer Register(1)
U-0
U-0
U-0
U-0
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHSPTR<15:8>(2)
bit 15

bit 8

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHSPTR<7:0>(2)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHSPTR<15:0>: Channel Source Pointer bits(2)
1111111111111111 = Points to byte 65,535 of the source
•
•
•
0000000000000001 = Points to byte 1 of the source
0000000000000000 = Points to byte 0 of the source

Note 1:
2:

r = Reserved bit

When in Pattern Detect mode, this register is reset on a pattern detect.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

DS61117F-page 31-26

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

—

—

—

—

—

—

U-0

U-0

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHDPTR<15:8>(1)
bit 15

bit 8

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHDPTR<7:0>(1)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHDPTR<15:0>: Channel Destination Pointer bits(1)
1111111111111111 = Points to byte 65,535 of the destination
•
•
•
0000000000000001 = Points to byte 1 of the destination
0000000000000000 = Points to byte 0 of the destination

Note 1:

r = Reserved bit

Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-27

DMA Controller

Register 31-15: DCHxDPTR: DMA Channel x Destination Pointer Register
U-0
U-0
U-0
U-0
U-0
U-0

31

PIC32MX Family Reference Manual
Register 31-16: DCHxCSIZ: DMA Channel x Cell-Size Register(1,2,3)
U-0
U-0
U-0
U-0
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHCSIZ<15:8>(4)
bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHCSIZ<7:0>(4)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHCSIZ<15:0>: Channel Cell-Size bits(4)
1111111111111111 = 65,535 bytes transferred on an event
•
•
•
0000000000000010 = 2 bytes transferred on an event
0000000000000001= 1 byte transferred on an event
0000000000000000 = 65,536 bytes transferred on an event

Note 1:

2:

3:

4:

r = Reserved bit

This register has an associated Clear register (DCHxCSIZCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxCSIZSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxCSIZINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

DS61117F-page 31-28

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHCPTR<15:8>(2)
bit 15

bit 8

R-0

R-0

R-0

R-0

R-0

R-0

R-0

R-0

CHCPTR<7:0>(2)
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

r = Reserved bit

bit 31-16

Unimplemented: Read as ‘0’

bit 15-0

CHCPTR<7:0>: Channel Cell Progress Pointer bits(2)
1111111111111111 = 65,535 bytes have been transferred since the last event
•
•
•
0000000000000001 = 1 byte has been transferred since the last event
0000000000000000 = 0 bytes have been transferred since the last event

Note 1:
2:

When in Pattern Detect mode, this register is reset on a pattern detect.
Depending on the device variant, not all bits are available. Refer to the specific device data sheet for more
details.

© 2010 Microchip Technology Inc.

DS61117F-page 31-29

DMA Controller

Register 31-17: DCHxCPTR: DMA Channel x Cell Pointer Register(1)
U-0
U-0
U-0
U-0
U-0

31

PIC32MX Family Reference Manual
Register 31-18: DCHxDAT: DMA Channel x Pattern Data Register(1,2,3)
U-0
U-0
U-0
U-0
U-0
—

—

—

—

—

U-0

U-0

U-0

—

—

—

bit 31

bit 24

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 23

bit 16

U-0

U-0

U-0

U-0

U-0

U-0

U-0

U-0

—

—

—

—

—

—

—

—

bit 15

bit 8

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

R/W-0

CHPDAT<7:0>
bit 7

bit 0

Legend:
R = Readable bit

W = Writable bit

P = Programmable bit

U = Unimplemented bit

-n = Bit Value at POR: (‘0’, ‘1’, x = Unknown)

r = Reserved bit

bit 31-8

Unimplemented: Read as ‘0’

bit 7-0

CHPDAT<7:0>: Channel Data Register bits
Pattern Terminate mode:
Data to be matched must be stored in this register to allow terminate on match.
All other modes:
Unused.

Note 1:

2:

3:

This register has an associated Clear register (DCHxDATCLR) at an offset of 0x4 bytes. Writing a ‘1’ to
any bit position in the Clear register will clear valid bits in the associated register. Reads from the Clear
register should be ignored.
This register has an associated Set register (DCHxDATSET) at an offset of 0x8 bytes. Writing a ‘1’ to any
bit position in the Set register will set valid bits in the associated register. Reads from the Set register
should be ignored.
This register has an associated Invert register (DCHxDATINV) at an offset of 0xC bytes. Writing a ‘1’ to
any bit position in the Invert register will invert valid bits in the associated register. Reads from the Invert
register should be ignored.

DS61117F-page 31-30

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
MODES OF OPERATION

DMA Controller

31.3

The DMA module offers the following operating modes:
•
•
•
•
•

Basic Transfer mode
Pattern Match Termination mode
Channel Chaining mode
Channel Auto-Enable mode
Special Function Module (SFM) mode: LFSR CRC, IP header checksum

Note that these operation modes are not mutually exclusive, but can be simultaneously
operational. For example, the DMA controller can perform CRC calculation using chained
channels and terminating the transfer upon a pattern match.
The following terminology is used while describing the various operational modes of the DMA
Controller:
Event: Any system event that can initiate or abort a DMA transfer.
Transaction: A single word transfer (up to 4 bytes), comprised of read and write operations.
Cell Transfer: The number of bytes transferred when a DMA channel has a transfer initiated
before waiting for another event (given by the DCHxCSIZ register). A cell transfer is comprised
of one or more transactions.
Block Transfer: Defined as the number of bytes transferred when a channel is enabled. The
number of bytes is the larger of either DCHxSSIZ or DCHxDSIZ. A block transfer is comprised
of one or more cell transfers.

31.3.1

Basic Transfer Mode

A DMA channel will transfer data from a source register to a destination register without CPU
intervention. The Channel Source Start Address register (DCHxSSA) defines the physical start
address of the source. The Channel Destination Start Address register (DCHxDSA) defines the
physical start address of the destination. Both the source and destination are independently
configurable using the DCHxSSIZ and DCHxDSIZ registers.
A cell transfer is initiated in one of two ways:
• Software can initiate a transfer by setting the channel CFORCE bit (DCHxECON<7>)
• Interrupt event occurs on the device that matches the CHSIRQ interrupt and SIRQEN = 1
(DCHxECON<4>). The user can select any interrupt on the device to start a DMA transfer
A DMA transfer will transfer DCHxCSIZ (cell transfer) bytes when a transfer is initiated (an
event occurs). The channel remains enabled until the DMA channel has transferred the larger of
DCHxSSIZ and DCHxDSIZ (i.e., block transfer is complete). If DCHxCSIZ is greater than the
larger of DCHxSSIZ and DCHxDSIZ, then the larger of DCHxSSIZ and DCHxDSIZ bytes will be
transferred. When the channel is disabled, further transfers will be prohibited until the channel is
re-enabled (CHEN is set to ‘1’).
Each channel keeps track of the number of words transferred from the source and destination
using the pointers DCHxSPTR and DCHxDPTR. Interrupts are generated when the source or
Destination Pointer is half of the size (DCHxSSIZ/2 or DCHxDSIZ/2), or when the source or
destination counter reaches the end. These interrupts are CHSHIF (DCHxINT<6>), CHDHIF
(DCHxINT<4>), CHSDIF (DCHxINT<7>) or CHDDIF (DCHxINT<5>), respectively.
A DMA transfer request can be reset by the following:
• Writing the CABORT bit (DCHxECON<6>)
• Pattern match occurs if pattern match is enabled as described in 31.3.2 “Pattern Match
Termination Mode”, provided that Channel Auto-Enable mode bit CHAEN
(DCHxCON<4>), is not set
• Interrupt event occurs on the device that matches the CHAIRQ <7:0> bits (DCHxECON<23:16>)
interrupt if enabled by AIRQEN bit (DCHxECON<3>)
• Detection of an address error
• Completion of a cell transfer
• A block transfer completes and the Channel Auto-Enable mode (CHAEN) is not set

© 2010 Microchip Technology Inc.

31

DS61117F-page 31-31

PIC32MX Family Reference Manual
When a channel abort interrupt occurs, the Channel Transfer Abort Interrupt Flag CHTAIF bit
(DCHxINT<1>) is set. This allows the user to detect and recover from an aborted DMA transfer.
When a transfer is aborted, any transaction currently underway will be completed.
The Source and Destination Pointers are updated as a transfer progresses. These pointers are
read-only. The pointers are reset under the following conditions:
• If the channel source address (DCHxSSA) is updated, the Source Pointer (DCHxSPTR)
will be reset
• Similar updates to the destination address (DCHxDSA) will cause the Destination Pointer
(DCHxDPTR) to be reset
• A channel transfer is aborted by writing the CABORT bit (DCHxECON<6>)
Note:
Example 31-1:

Refer to Table 31-5 for more detailed information about the channel event behavior.

DMA Channel Initialization for Basic Transfer Mode Code Example

/*
The following code example illustrates the DMA channel 0 configuration for a data transfer.
*/
IEC1CLR=0x00020000;
// disable DMA channel 0 interrupts
IFS1CLR=0x00020000;
// clear existing DMA channel 0 interrupt flag
IEC1CLR=0x00010000;
// disable DMA channel 0 interrupts
IFS1CLR=0x00010000;
// clear existing DMA channel 0 interrupt flag
DMACONSET=0x00008000;
DCH0CON=0x3;

// enable the DMA controller
// channel off, pri 3, no chaining

CH0ECON=0;

// no start or stop irq’s, no pattern match

DCH0SSA=0x1d010000;
DCH0DSA=0x1d020000;
DCH0SSIZ=200;
DCH0DSIZ=200;
DCH0CSIZ=200;

//
//
//
//
//
//

DCH0INTCLR=0x00ff00ff;
DCH0CONSET=0x80;

// clear existing events, disable all interrupts
// turn channel on

DCH0ECONSET=0x00000080;

// initiate a transfer
// set CFORCE to 1

program the transfer
transfer source physical address
transfer destination physical address
source size 200 bytes
destination size 200 bytes
200 bytes transferred per event

// do something else
// poll to see that the transfer was done
while(TRUE)
{
register int pollCnt;

int dmaFlags=DCH0INT;
if( (dmaFlags&0xb)
{
break;
}
pollCnt=100;
while(pollCnt--);

// use a poll counter.
// continuously polling the DMA controller in a tight
// loop would affect the performance of the DMA transfer

// one of CHERIF (DCHxINT<0>), CHTAIF (DCHxINT<1>)
// or CHBCIF (DCHxINT<3>) flags set
// transfer completed
// use an adjusted value here
// wait before reading again the DMA controller

}
// check the transfer completion result

DS61117F-page 31-32

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Interrupt and Pointer Updates

The Source and Destination Pointers are updated after every transaction. Interrupts will also be
set or cleared at this time. If a pointer passes the halfway point during a transaction, the
interrupt will be updated accordingly.
Pointers are reset when any of the following occurs:
•
•
•
•

On any device Reset
When the DMA is turned off (ON bit (DMACON<15>)) is ‘0’
A block transfer completes, regardless of the state of CHAEN bit (DCHxCON<4>)
A pattern match terminates a transfer, regardless of the state of CHAEN bit
(DCHxCON<4>)
• The CABORT bit (DCHxECON<6>) flag is written
• Source or destination start addresses are updated

31.3.2

Pattern Match Termination Mode

Pattern Match Termination mode allows the user to end a transfer if a byte of data written during
a transaction matches a specific pattern, as defined by the DCHxDAT register. A pattern match
is treated the same way as a block transfer complete, where the CHBCIF bit (DCHxINT<3>) is
set and the CHEN bit (DCHxCON<7>) is cleared.
This feature is useful in applications where a variable data size is required and eases the set up
of the DMA channel. UART is a good example of where this can be effectively used.
Assuming a system has a series of messages that are routinely transmitted to an external host
and it has a maximum message size of 86 characters, the user would set the following
parameters on the channel:
• DCHxSSIZ to 87 bytes:
If something unexpected occurs the CPU program will be interrupted when the buffer
overflows and can take the appropriate action.
• DCHxDSIZ set to 1 byte.
• The destination address is set to the UART TXREG.
• The DCHxDAT is set to 0x00, which will stop the transfer on a NULL character in any byte
lane.
• The CHSIRQ bits (DCHxECON<15:8>) is set to the UART “transmit buffer empty” IRQ.
• The SIRQEN bit (DCHxECON<4>) is set to enable the channel to respond to the start
interrupt event.
• The start address is set to the start address of the message to be transferred.
• The channel is enabled, CHEN = 1 (DCHxCON<7>).
• The user will then force a cell transfer through CFORCE bit (DCHxECON<7>) and the first
byte transmission by the UART.
• Each time a byte is transmitted by the UART, the transmit buffer empty interrupt will initiate
the following byte transfer from the source to the UART.
• When the DMA channel detects a NULL character in any of the byte lanes of the channel,
the transaction will be completed and the channel disabled.
Pattern matching is independent of the byte lane of the source data. If ANY byte in the source
buffer matches DCHxDAT, a pattern match is detected. The transaction will be completed and
the data read from the source will be written to the destination.

© 2010 Microchip Technology Inc.

DS61117F-page 31-33

DMA Controller

31.3.1.1

31

PIC32MX Family Reference Manual
Example 31-2:

DMA Channel Initialization in Pattern Match Transfer Mode Code Example

/*
The following code example illustrates the DMA channel 0 configuration for data transfer with
pattern match enabled. Transfer from the UART1 a  ended string, at most 200 characters long
*/
IEC1CLR=0x00020000;
IFS1CLR=0x00020000;
IEC1CLR=0x00010000;
IFS1CLR=0x00010000;

//
//
//
//

DMACONSET=0x00008000;
DCH0CON=0x03;

// enable the DMA controller
// channel off, priority 3, no chaining

DCH0ECON=(27 <<8)| 0x30;
DCH0DAT=’\r’;

// start irq is UART1 RX, pattern match enabled
// pattern value, carriage return

DCH0SSA=VirtToPhys(&U1RXREG);
DCH0DSA=0x1d020000;
DCH0SSIZ=1;
DCH0DSIZ=200;
DCH0CSIZ=1;

//
//
//
//
//
//

DCH0INTCLR=0x00ff00ff;
DCH0INTSET=0x00090000;

// clear existing events, disable all interrupts
// enable Block Complete and error interrupts

IPC9CLR=0x00001f00;
IPC9SET=0x00001600;
IPC9CLR=0x0000001f;
IPC9SET=0x00000016;
IEC1SET=0x00020000;
IEC1SET=0x00010000;

//
//
//
//
//
//

DCH0CONSET=0x80;

// turn channel on

DS61117F-page 31-34

disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag
disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag

program the transfer
transfer source physical address
transfer destination physical address
source size is 1 byte
destination size at most 200 bytes
one byte per UART transfer request

clear the DMA channel 0 priority and sub-priority
set IPL 5, sub-priority 2
clear the DMA channel 0 priority and sub-priority
set IPL 5, sub-priority 2
enable DMA channel 0 interrupt
enable DMA channel 0 interrupt

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Channel Chaining Mode

Channel chaining is an enhancement to the DMA channel operation. A channel (slave channel)
can be chained to an adjacent channel (master channel). The slave channel will be enabled
when a block transfer of the master channel completes (i.e., CHBCIF bit (DCHxINT<3>) is set).
At this point, any event on the slave channel will initiate a cell transfer. If the channel has an
event pending, a cell transfer will begin immediately.
The master channel will set its interrupt flags normally, CHBCIF bit (DCHxINT<3>) and has no
knowledge of the “chain” status of the slave channel. The master channel is still able to cause
interrupts at the end of a DMA transfer if one of the CHSDIE/CHDDIE/CHBCIE bits
(DCHxINT<23/21/19>) is set.
In the channels natural priority order, channel 0 has the highest priority and channel 7 the
lowest. The channel higher or lower in natural priority, that can enable a specific channel, is
selected by CHCHNS bit (DCHxCON<8>), provided that channel chaining is enabled,
CHCHN = 1 (DCHxCON<5>).
Note:

In some devices, channel 0 has the highest priority and channel 4 the lowest. Refer
to the specific device data sheet for availability.

A feature of the DMA module is the ability to allow events while the channel is disabled using
the CHAED bit (DCHxCON<6>). This bit is particularly useful in Chained mode, in which the
slave channel needs to be ready to start a transfer as soon as the channel is enabled by the
master channel.
The following examples demonstrate situations in which chaining may be useful:
1.

2.

Transferring data in one peripheral (e.g., from UART1, DMA channel 0, at 9600 baud, to
SRAM) to another peripheral (e.g., from SRAM to UART2, DMA channel 1, at
19200 baud).
In this example, CHAED will be set in both channels; with UART2 setting the event detect,
CHEDET bit (DCHxCON<2>), on channel 1 when the last byte has been transmitted. As
soon as channel 0 completes a transfer, channel 1 is enabled and the data is
transferred immediately.
A/D converter transfers data to one buffer (connected to channel 0).
When the destination buffer 0 is full (block transfer completes), channel 1 is enabled and
further conversions are transferred to buffer 1. In this case, CHAED will not be enabled. If
it were, the last word transferred by channel 0 would be transferred a second time by
channel 1 (because the A/D converter interrupt event would have set the event detect flag
CHEDET in both channels).

© 2010 Microchip Technology Inc.

DS61117F-page 31-35

DMA Controller

31.3.3

31

PIC32MX Family Reference Manual
Example 31-3:

DMA Channel Initialization in Chaining Mode Code Example

/*
The following code example illustrates the DMA channel 0 configuration for data transfer with
pattern match enabled. DMA channel 0 transfer from the UART1 to a RAM buffer while DMA channel 1
transfers data from the RAM buffer to UART2. Transferred strings are at most 200 characters
long. Transfer on UART2 will start as soon as the UART1 transfer is completed.
*/
unsigned char myBuff<200>;

// transfer buffer

IEC1CLR=0x00020000;
IFS1CLR=0x00020000;
IEC1CLR=0x00010000;
IFS1CLR=0x00010000;

//
//
//
//

DMACONSET=0x00008000;

// enable the DMA controller

DCH0CON=0x3;
DCH1CON=0x62;

//
//
//
//

DCH0ECON=(27 <<8)| 0x30;
DCH1ECON=(42 <<8)| 0x30;

// start IRQ is UART1 RX, pattern enabled
// start IRQ is UART1 TX, pattern enabled

DCH0DAT=DCH1DAT=’\r’;

// pattern value, carriage return

DCH0SSA=VirtToPhys(&U1RXREG);
DCH0DSA=VirtToPhys(myBuff);
DCH0SSIZ=1;
DCH0DSIZ=200;
DCH0CSIZ=1;

//
//
//
//
//
//

program channel 0 transfer
transfer source physical address
transfer destination physical address
source size is 1 byte
dst size at most 200 bytes
one byte per UART transfer request

DCH1SSA=VirtToPhys(myBuff);
DCH1DSA=VirtToPhys(&U2TXREG);
DCH1SSIZ=200;
DCH1DSIZ=0;
DCH1CSIZ=1;

//
//
//
//
//
//

program channel 1 transfer
transfer source physical address
transfer destination physical address
source size at most 200 bytes
dst size is 1 byte
one byte per UART transfer request

DCH0INTCLR=0x00ff00ff;
DCH1INTCLR=0x00ff00ff;
DCH1INTSET=0x00090000;

// DMA0: clear events, disable interrupts
// DMA1: clear events, disable interrupts
// DMA1: enable Block Complete and error interrupts

IPC9CLR=0x001f1f00;

IEC1SET=0x00040000;
IEC1SET=0x00020000;

//
//
//
//
//
//
//
//
//
//

DCH0CONSET=0x80;

// turn channel on

IPC9SET=0x000b1600;
IPC9CLR=0x00001f1f;
IPC9SET=0x00000b16;

DS61117F-page 31-36

disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag
disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag

channel 0 off, priority 3, no chaining
channel 1 off, priority 2
chain to higher priority
(channel 0), enable events detection while disabled

clear the DMA channels 0 and 1 priority and
sub-priority
set IPL 5, sub-priority 2 for DMA channel 0
set IPL 2, sub-priority 3 for DMA channel 1
clear the DMA channels 0 and 1 priority and
sub-priority
set IPL 5, sub-priority 2 for DMA channel 0
set IPL 2, sub-priority 3 for DMA channel 1
enable DMA channel 1 interrupt
enable DMA channel 1 interrupt

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Channel Auto-Enable Mode

The channel auto-enable can be used to keep a channel active, even if a block transfer
completes or pattern match occurs. This prevents the user from having to re-enable the channel
each time a block transfer completes. To use this mode the user will configure the channel,
setting the CHAEN bit (DCHxCON<4>) before enabling the channel (i.e., setting the CHEN bit
(DCHxCON<7>)). The channel will behave as normal except that normal termination of a
transfer will not result in the channel being disabled.
Normal block transfer completion is defined as:
• Block Transfer Complete
• Pattern Match Detect
As before, the Channel Pointers will be reset. This mode is useful for applications that do
repeated pattern matching.
Note:

© 2010 Microchip Technology Inc.

The CHAEN bit prevents the channel from being automatically disabled once it has
been enabled. The channel will still have to be enabled by the software.

DS61117F-page 31-37

DMA Controller

31.3.4

31

PIC32MX Family Reference Manual
31.3.5

Special Function Module (SFM) Mode

The DMA module has one integrated Special Function Module (SFM) shared by all channels.
As illustrated in Figure 31-4, the SFM has the following blocks:
•
•
•
•

LFSR CRC
IP Header Checksum
Byte Reordering
Bit Reordering

Figure 31-4:

Special Function Module (SFM)
Data In

Byte
Reordering

BYTO

Bit
Reordering

BITO

LFSR CRC

IP Header
Checksum
00
01

CRCDATA

Data Out

10
CRCAPP
Note: CRCAPP = 1; WBO = 1 is invalid.

WBO

Depending on the device variant, the SFM is a highly configurable, 16-bit or 32-bit CRC
generator. The SFM can be assigned to any available DMA channel by setting the CRCCH bits
(DCRCCON<2:0>) appropriately. The SFM is enabled by setting the CRCEN bit
(DCRCCON<7>).
The data from the source can be optionally subjected to byte reordering using the WBO bit. The
data is then optionally passed to the LFSR CRC or IP header checksum blocks based on the
setting of the CRCTYP bit (DCRCCON<15>), as illustrated in Figure 31-4.
Further, the SFM modifies the behavior of the DMA channel associated with the SFM. The
behavior of the channel is selected by the CRCAPP bit (DCRCCON<6>), resulting in the
following two modes:
• Background Mode: CRC is calculated in the background, with normal DMA behavior
maintained (see 31.3.5.1 “CRC Background Mode (CRCAPP = 0)”).
• Append Mode: Data read from the source is not written to the destination, but the CRC data
is accumulated in the CRC data register. The accumulated CRC is written to the location
given by DCHxDSA when a block transfer completes (see 31.3.5.2 “CRC Append Mode
(CRCAPP = 1)”).
The order in which data is written to the destination can be selected using the WBO bit
(DCRCCON<27>). If the WBO bit is cleared, the writes to the destination are unaltered. If the
WBO bit is set, the writes to the destination are reordered as defined by the CRC Byte Order
Selection (BYTO<1:0>) bits (DCRCCON<29:28>).
Note:

DS61117F-page 31-38

This feature is not available on all devices. Refer to the specific device data sheet
for availability.

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

Note that when in IP Header Checksum mode (CRCTYP = 1), data written reads back as the
1’s complement form as this is the current value of the checksum.
The CRC value in DCRCDATA can be read at any time during the CRC generation, but is only
valid once the transfer completes.
Note 1: If a DMA Transfer is aborted while a CRC calculation is in progress, the DMA channel should be reset before the next CRC calculation is started. Alternatively, the
same channel or another unused channel can be configured to transfer two or more
bytes. The transfer should then be initiated and allowed to complete. The CRC
module is then ready for the next CRC calculation.
2: If a DMA channel is disabled (CHEN = 0) when a CRC calculation is in progress,
the value in the DCRCDATA register is not updated. The same channel or another
unused channel can be configured to transfer two or more bytes. The transfer
should then be initiated and allowed to complete. When the transfer is complete,
the DCRCDATA value will be correct for the number of byte processed prior to the
stop being issued. The DMA address register can be inspected to determine the
address range of the current CRC value.

31.3.5.1

CRC BACKGROUND MODE (CRCAPP = 0)

In this mode, the behavior of the DMA channel is maintained. The DMA reads the data from the
source, passes it through the CRC module and writes it to the destination. Writes to the
destination obey the WBO selection. In this mode, the calculated CRC is left in the DCRCDATA
register at the end of the block transfer.
This mode can be used to calculate a CRC as data is moved from a source address to a
destination address. The data source can be either a memory buffer or a FIFO in a peripheral.
Likewise, the destination can be either a memory buffer or a FIFO. When the data transfer
completes, the user can read the calculated CRC value and either append it to the transmitted
data or verify the received CRC data.
Background mode potentially ties up the CRC module for extended periods of time. For instance,
when assigned to a UART data stream, the SFM cannot be used by another channel until the
UART data stream completes.

© 2010 Microchip Technology Inc.

DS61117F-page 31-39

DMA Controller

The SFM generator can be seeded by writing to the DCRCDATA register before enabling the
channel.

31

PIC32MX Family Reference Manual
Example 31-4:

DMA LFSR CRC Calculation in Background Mode Code Example

/*
The following code example illustrates a DMA calculation using the CRC background mode. Data is
transferred from a 200 bytes Flash buffer to a RAM buffer and the CRC is calculated while the
transfer takes place. */
unsigned int blockCrc;

// CRC of the flash block

IEC1CLR=0x00020000;
IFS1CLR=0x00020000;
IEC1CLR=0x00010000;
IFS1CLR=0x00010000;

//
//
//
//

DMACONSET=0x00008000;

// enable the DMA controller

DCRCDATA=0xffff;
DCRCXOR=0x1021;
DCRCCON=0x0f80;

//
//
//
//

DCH0CON=0x03;
DCH0ECON=0;

// channel off, priority 3, no chaining
// no start irqs, no match enabled

DCH0SSA=VirtToPhys(flashBuff);
DCH0DSA=VirtToPhys(ramBuff);
DCH0SSIZ=200;
DCH0DSIZ=200;
DCHOCSIZ=200;

//
//
//
//
//
//

DCH0INTCLR=0x00ff00ff;

// DMA0: clear events, disable interrupts

DCH0CONSET=0x80;

// channel 0 on

DCH0ECONSET=0x00000080;

// initiate a transfer
// set CFORCE to 1

disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag
disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag

seed the CRC generator
Use the standard CCITT CRC 16 polynomial: X^16+X^12+X^5+1
CRC enabled, polynomial length 16, background mode
CRC attached to the DMA channel 0.

program channel transfer
transfer source physical address
transfer destination physical address
source size
destination size
200 bytes per event

// do something else while the transfer takes place
//
BOOL error=FALSE;
while(TRUE)
{
register int pollCnt;
//
int dmaFlags=DCH0INT;
if( (dmaFlags& 0x3)
{
//
error=TRUE;
//
break;
}
else if (dmaFlags&0x8)
{
//
break;
//
}
pollCnt=100;
//
while(pollCnt--);
//
}
if(!error)
{
blockCrc=DCRDATA;
}
else
{

poll to see that the transfer was done

don’t poll in a tight loop

CHERIF (DCHxINT<0>) or CHTAIF (DCHxINT<1> set
error or aborted...

CHBCIF (DCHxINT<3>) set
transfer completed normally
use an adjusted value here
wait before polling again

// read the CRC of the transferred flash block

// process error
}

DS61117F-page 31-40

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
CRC APPEND MODE (CRCAPP = 1)

In this mode, the DMA only feeds source data to the CRC module; it does not write source data
to the destination address. However, when the block transfer completes or a pattern match
occurs, the DMA writes the CRC value to the destination address.
This mode is best used when multiple peripherals are required to use the CRC generator. In this
case, the input data is accumulated in a buffer on the device. Once the buffer is complete the
CRC is generated on the buffer and used appropriately. Because the DMA does not need to wait
for multiple events (typically interrupts) a block of data is passed through the CRC in fairly short
order, allowing the CRC module to be assigned to a different channel, or redirected to a different
block of data.
The following usage notes apply to CRC Append mode:
• Only the source buffer is viewed when considering whether a block transfer is complete,
the destination address (DCHxDSA) is only used as the location to write the generated
CRC value.
• The destination size (DCHxDSIZ) can be a maximum of 4.
- If DCHxDSIZ is greater than 4, only 4 bytes are written
- If DCHxDSIZ is less than 4, only DCHxDSIZ bytes of the CRC are written
- PLEN bit has no effect on the number of CRC bytes or bits written
• After the write, the channel is disabled.
• Any abort (i.e., abort IRQ asserts) prevents the CRC value from being written
• Reordering is not supported in Append mode if WBO bit is set to ‘0’.

© 2010 Microchip Technology Inc.

DS61117F-page 31-41

DMA Controller

31.3.5.2

31

PIC32MX Family Reference Manual
Example 31-5:

CRC Calculation in Append Mode Code Example

/*
The following code example illustrates a DMA calculation using the CRC append mode. The CRC of
a 256 bytes flash buffer is calculated without performing any data transfer. As soon as the CRC
calculation is completed the CRC value of the flash buffer is available in a local variable for
further use. */
unsigned int blockCrc;

// CRC of the flash block

IEC1CLR=0x00020000;
IFS1CLR=0x00020000;
IEC1CLR=0x00010000;
IFS1CLR=0x00010000;

//
//
//
//

DMACONSET=0x00008000;

// enable the DMA controller

DCRCDATA=0xffff;
DCRCXOR=0x1021;
DCRCCON=0x0fc0;

//
//
//
//

DCH0CON=0x03;
DCH0ECON=0;

// channel off, priority 3, no chaining
// no start irqs, no match enabled

DCH0SSA=VirtToPhys(flashBuff);
DCH0DSA=VirtToPhys(&blockCrc);
DCH0SSIZ=200;
DCH0DSIZ=200;
DCHOCSIZ=200;

//
//
//
//
//
//

DCH0INTCLR=0x00ff00ff;
DCH1INTCLR=0x00ff00ff;

// DMA0: clear events, disable interrupts
// DMA1: clear events, disable interrupts

DCH0CONSET=0x80;

// channel 0 on

DCH0ECONSET=0x00000080;

// initiate a transfer
// set CFORCE to 1

disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag
disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag

seed the CRC generator
Use the standard CCITT CRC 16 polynomial: X^16+X^12+X^5+1
CRC enabled, polynomial length 16, append mode
CRC attached to the DMA channel 0.

program channel transfer
transfer source physical address
transfer destination physical address
source size
dst size
200 bytes transferred per event

// do something else while the CRC calculation takes place
//
BOOL error=FALSE;
while(TRUE)
{
register int pollCnt;
//
int dmaFlags=DCH0INT;
if( (dmaFlags& 0x3)
{
//
error=TRUE;
//
break;
}
else if (dmaFlags&0x8)
{
//
break;
//
}
pollCnt=100;
//
while(pollCnt--);
//
}

poll to see that the transfer was done

don’t poll in a tight loop

CHERIF (DCHxINT<0>) or CHTAIF (DCHxINT<1> set
error or aborted...

CHBCIF (DCHxINT<3>) set
transfer completed normally
use an adjusted value here
wait before polling again

if(error)
{
// process error
}

DS61117F-page 31-42

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
DATA ORDER

Data read from the source can be reordered to allow for variations in the byte order of the source
data, such as endianness. The reordered source data is written to the channel destination when
WBO = 1. The unaltered source data is written to the destination when WBO = 0.
The CRC calculation takes place, even if the user does not utilize the result stored in
DCRCDATA.
BYTO controls the byte order of the data being processed by the module. Figure 31-5 shows the
different byte order settings and the effect on data reads. BYTO value of ‘01’ is useful for
reordering bytes within words. BYTO values of ‘10’ and ‘11’ are useful for reordering bytes within
half-words.
It is important to note that the data is reordered as it is read. This means that data that is not
word-aligned may not be reordered correctly.
When using the LFSR CRC mode or IP Header Checksum mode of the SFM, the bit order can
be changed by using the BITO bit.
Figure 31-5:

Byte Order for BYTO Values
BYTO=00

BYTO=10

Byte3

Byte2

Byte1

Byte0

Byte3

Byte2

Byte1

Byte0

Byte3

Byte2

Byte1

Byte0

Byte1

Byte0

Byte3

Byte2

BYTO=01

BYTO=11

Byte3

Byte2

Byte1

Byte0

Byte3

Byte2

Byte1

Byte0

Byte0

Byte1

Byte2

Byte3

Byte2

Byte3

Byte0

Byte1

31.3.5.4

LFSR CRC

The CRC generator will take one system clock to process each byte of data read from the
source. This implies that if 32 bits of data are read from the source, the CRC generation will take
four system clocks to process the data.
When the CRYTYP bit is cleared, the SFM is set to LFSR CRC mode and calculates the LFSR
CRC.
Note:

This feature is not available on all devices. Refer to the specific device data sheet
for availability.

The implementation of the CRC module is software configurable. The terms of the polynomial
and its length can be programmed using the DCRCXOR<31:0> bits and the PLEN<4:0> bits
(DCRCCON<12:8>), respectively.
Example 31-6 and Example 31-7 show the polynomials for the 16-bit and 32-bit CRC.
Example 31-6:

16-bit CRC Polynomial
x

Example 31-7:
x

© 2010 Microchip Technology Inc.

31

16

+x

12

+x +1

5

+x

11

+x

32-bit CRC Polynomial
+x

26

+x

23

+x

22

+x

16

+x

12

10

8

7

5

4

2

+x +x +x +x +x +x+1

DS61117F-page 31-43

DMA Controller

31.3.5.3

31

PIC32MX Family Reference Manual
To program either polynomial into the CRC generator, the CRC register bits should be set as
shown in the following table:
Table 31-2:

Example CRC Setup

CRC Type

Bit Name

Bit Value

Devices with
16-bit CRC

PLEN<3:0>
DCRCXOR<15:0>
PLEN<4:0>
DCRCXOR<31:0>

‘b1111
‘b0001 0000 0010 000
‘b11111
‘b0000 0100 1100 0001 0001 1101 1011 0110

Devices with
32-bit CRC

The PLEN<4:0> bits (DCRCCON<12:8>) in the CRC generator are used to select which bit is
used as the feedback point of the CRC. For a 16-bit CRC example, if PLEN<4:0> = 0x0110, bit
6 of the Shift register is fed into the XOR gates of all bits set in the CRCXOR register.
The CRCXOR feedback points are specified using the DCRCXOR register. Setting the Nth bit in
the DCRCXOR register will enable the input to the Nth bit of the CRC Shift register to be XORed
with the (PLEN + 1)th bit of the CRC Shift register. Bit 0 of the CRC generator is always XORed.

31.3.5.5

CALCULATING THE IP HEADER CHECKSUM

When the CRCTYP bit is set, the SFM calculates the IP header checksum. Use the following
procedure to calculate the IP header checksum:
1.
2.
3.
4.
5.
6.

Configure a channel to point to the IP header.
Configure CRCCON to enable the SFM and select the channel being used.
Set the CRCTYP bit (DCRCCON<15>), which selects IP Header checksum.
Set DCRCDATA to ‘0000’.
Start the transfer.
When the transfer completes, read the data out of the DCRCDATA register.
Note:

31.3.6

This feature is not available on all devices. Refer to the specific device data sheet
for availability.

Suspending Transfers

The user application can immediately suspend the DMA module by writing the SUSPEND bit
(DMACON<12>). This will immediately suspend the DMA controller from any further bus
transactions.
Depending on the device variant, when the DMA module is suspended by setting the
SUSPEND bit, the user application should poll the DMABUSY bit (DMACON<11>) to determine
when the module is completely suspended following the completion of the current transaction.
Note:

The DMABUSY bit is not available on all device. Refer to the specific device data
sheet for availability.

Individual channels may be suspended using the CHEN bit (DCHxCON<7>). If a DMA transfer
is in progress and the CHEN bit is cleared, the current transaction will be completed and further
transactions on the channel will be suspended.
Depending on the device variant, when the channel is suspended by clearing the CHEN bit, the
user application should poll the CHBUSY bit (DCHxCON<15>) to determine when the channel
is completely suspended following completion of the current transaction.
Clearing the enable bit (CHEN) will not affect the Channel Pointers or the transaction counters.
While a channel is suspended, the user can elect to continue to receive events (abort interrupts,
etc.) by setting CHAED bit (DCHxCON<6>).

DS61117F-page 31-44

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Resetting the Channel

The channel logic will be reset on any device Reset. The channel is also reset when the channel
flag bit CABORT (DCHxECON<6>) is written. This will turn off channel flag bit CHEN = 0, clear
the Source and Destination Pointers, and reset the event detector. When the CABORT bit is set,
the current transaction in progress (if any) will complete before the channel is reset, but any
remaining transactions will be aborted.
The user should modify the channel registers only while the channel is disabled (CHEN = 0).
Modifying the Source and Destination registers will reset the corresponding pointer registers
(DCHxSPTR or DCHxDPTR).
Note:

31.3.8

The channel size must be changed while the channel is disabled.

Channel Priority and Selection

The DMA controller has a natural priority associated with each of the channels. Channel 0 has
the highest natural priority. The channel priority is defined by CHPRI<1:0> bits (DCHxCON<1:0>). These bits identify the channel’s priority. When multiple channels have transfers
pending, the next channel to transmit data will be selected as follows:
• Channels with the highest priority will complete all cell transfers before moving onto
channels with a lower priority (see behavior, “PRI3 xfers”, in Figure 31-6).
• If multiple channels have the same priority (identical CHPRI), the controller will cycle
through all channels at that priority. Each channel with a cell transfer in progress at the
highest priority will be allowed a single transaction of the active cell transfer before the
controller allows a single transaction by the next channel at that priority level (see behavior,
“PRI2 xfers” between markers “C” and “B”, in Figure 31-6).
• If a channel with a higher priority requests a transfer while another channel of lower priority
has a transaction in process, the transaction will complete before moving to the channel
with the higher priority (see events at markers “A” in Figure 31-6).
Figure 31-6:

Channel Priority Behavior

REQ: CH0, PRI0
REQ: CH1, PRI2
REQ: CH2, PRI3
REQ: CH3, PRI2
DMA Active Channel

none

0

3

PRI0
xfers

2

PRI2
xfers

A

2

2

3

3

1

PRI3 xfers

A

3

1

0
PRI0
xfers

PRI2 xfers

B

C

Cycle through
CH1 and CH3

none

B

Transition Legend:
A – Higher priority transfer request; suspend current and transfer next.
B – All highest priority transfers complete; drop to channels at lower priority.
C – Cycle through all channels at the current priority.

© 2010 Microchip Technology Inc.

DS61117F-page 31-45

DMA Controller

31.3.7

31

PIC32MX Family Reference Manual
31.3.9

Byte Alignment

The byte alignment feature of the DMA controller relieves the user from aligning the source and
destination addresses.The read portion of a transaction will read the maximum number of bytes
that are available to be read in a given word. For example, if the Source Pointer is N > 4 bytes
from the source size, 4 bytes will be read if the Source Pointer points to byte 0, 3 bytes if the
Source Pointer points to byte 1, etc. If the number of bytes remaining in the source is N < 4, only
the first N bytes are read. This is important when the read includes registers that are updated on
a read.
The Source Pointer and Destination Pointers are updated after every write, with the number of
bytes that have been written. The user should note that in cases where a transfer is aborted,
before a transaction is complete, the Source Pointer will not necessarily reflect the reads that
have taken place.
An example of this behavior is given in Table 31-3. Example 1 demonstrates a simple transfer of
9 bytes between two large buffers, in which CHxSSA = 0x1000, CHxSSIZ = 100,
CHxDSA = 0x43F9, CHxDSIZ = 100 and CHxCSIZ = 9.
Table 31-3:

Source and Destination Pointer Updates – Example 1

Transaction Operation

Source Destination Transfer
Read
Write
Pointer
Pointer
Count/Size Address Address

Read Data(1)

Write Data(2)
YY_YY_YY_YY

1

Read

9

11

0/9

1009

xxxx(4)

33_22_11_XX

1

Write1

9

11

0/9

1009

440A

33_22_11_XX

22_11_YY_YY

1

Ptr
Update(3)

B

13

2/9

1009

440A

33_22_11_XX

YY_YY_YY_YY

1

Write2

B

13

2/9

1009

440C

33_22_11_XX

YY_YY_YY_33

1

Ptr
Update(3)

C

14

3/9

1009

440C

33_22_11_XX

YY_YY_YY_YY

2

Read

C

14

3/9

100C

440C

77_66_55_44

YY_YY_YY_YY

2

Write1

C

14

3/9

100C

440D

77_66_55_44

66_55_44_YY

2

Ptr
Update(3)

F

17

6/9

100C

440D

77_66_55_44

YY_YY_YY_YY

2

Write2

F

17

6/9

100C

4410

77_66_55_44

YY_YY_YY_77

2

Ptr
Update(3)

10

18

7/9

100C

4410

77_66_55_44

YY_YY_YY_YY

3

Read

10

18

7/9

1010

4410

XX_XX_99_88

YY_YY_YY_YY

3

Write1

10

18

7/9

1010

4411

XX_XX_XX_88

YY_99_88_YY

3

Ptr
Update(3)

12

1A

9/9

1010

4411

XX_XX_XX_88

YY_YY_YY_YY

Note 1:
2:
3:
4:

XX indicates that data read is discarded.
YY indicates that data that is NOT written.
Interrupts are updated when the pointers are updated as required.
Don’t care.

DS61117F-page 31-46

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

Table 31-4:

Source and Destination Pointer Updates – Example 2

Transaction Operation

Source Destination Transfer
Read
Write
Pointer
Pointer Count/Size Address Address

Read Data(1)

Write Data(2)

1

Read

9

0

0/8

1009

xxxx(4)

33_22_11_XX

YY_YY_YY_YY

1

Write1

9

0

0/8

1009

4402

33_22_11_XX

22_11_YY_YY

1

Ptr
Update(3)

B

2

2/8

1009

4402

33_22_11_XX

YY_YY_YY_YY

1

Write2

B

2

2/8

1009

4404

33_22_11_XX

YY_YY_YY_33

1

Ptr
Update(3)

C

3

3/8

1009

4404

33_22_11_XX

YY_YY_YY_YY

2

Read

C

3

3/8

100C

4404

77_66_55_44

YY_YY_YY_YY

2

Write1

C

3

3/8

100C

4405

77_66_55_44

YY_YY_44_YY

2

Ptr
Update(3)

D

0

4/8

100C

4405

77_66_55_44

YY_YY_YY_YY

2

Write2

D

0

4/8

100C

4402

77_66_55_44

66_55_YY_YY

2

Ptr
Update(3)

F

2

6/8

100C

4402

77_66_55_44

YY_YY_YY_YY

3

Write3

F

2

6/8

100F

4404

77_66_55_44

YY_YY_YY_77

3

Ptr
Update(3)

10

3

7/8

100F

4404

77_66_55_44

YY_YY_YY_YY

3

Read

10

18

7/8

1010

4404

BB_AA_99_88

YY_YY_YY_YY

3

Write1

10

18

7/8

1010

4405

BB_AA_99_88

YY_YY_88_YY

3

Ptr
Update(3)

11

1A

8/8

1010

4405

77_66_55_44

YY_YY_YY_YY

Note 1:
2:
3:
4:

XX indicates that data read is discarded.
YY indicates that data that is NOT written.
Interrupts are updated when the pointers are updated as required.
Don’t care.

31.3.10 Channel Transfer Behavior
Once a channel has been enabled, CHEN = 1 (DCHxCON<7>), any event that starts a cell
transfer will transfer the CHCSIZ (DCHxCSIZ) bytes of data. This will require one or more
transactions. Once the cell transfer is complete the channel will return to an inactive state, and
will wait for another channel start event to occur before starting another cell transfer.
When the larger of CHSSIZ (DCHxSSIZ) or CHDSIZ (DCHxDSIZ) bytes are transferred, a block
transfer completes, the channel transfer will be halted and the channel will be disabled (i.e.,
CHEN set to ‘0’ by hardware, and pointers are reset).

© 2010 Microchip Technology Inc.

DS61117F-page 31-47

DMA Controller

Another example of this behavior is given in Table 31-4. Example 2 demonstrates worst-case bus
utilization, i.e., unaligned buffers with destination buffer wrapping, in which CHxSSA = 0x1000,
CHxSSIZ = 100, CHxDSA = 0x4402, CHxDSIZ = 4 and CHxCSIZ = 8.

31

PIC32MX Family Reference Manual
31.3.11 Channel Enable
Each channel has an enable bit, CHEN, which can be used to enable or disable the channel in
question. When this bit is set, the channel transfer requests are serviced by the DMA controller.
When the CHEN bit is clear, the state of the channel is preserved (this allows the channel to be
suspended once a transfer has begun).
The CHEN bit will be cleared by hardware under the following conditions:
• A block transfer is complete, the pointer to the larger of the source or destination matches
the size (only if the CHAEN bit (DCHxCON<4>) is clear).
• A pattern match occurs in Pattern Match mode (only if the CHAEN bit is clear).
• An abort interrupt occurs.
• The user writes the CABORT bit (DCHxECON<6>).

31.3.12 Channel IRQ Detection
The DMA Controller maintains its own flags for detecting the start and abort IRQ in the system
and is completely independent of the INT Controller and IES/IFS flags. The corresponding IRQ
does not have to be enabled before a transfer can take place, nor cleared at the end of a DMA
transfer.
Once the start or abort IRQ system events are triggered, they will be detected automatically by
the DMA controller internal logic, without the need for user intervention.

31.3.13 Channel Event Transfer Initiation
A given channel transfer can be initiated by:
• Writing the CFORCE bit (DCHxECON<7>).
• An interrupt occurs that matches the value of CHSIRQ<7:0> (DCHxECON<15:8>) if it is
enabled by SIRQEN bit (DCHxECON<4>).
Channel events are registered if the channel is enabled (CHEN = 1), or if “Allow Event If
Disabled” is set (i.e., CHAED = 1 (DCHxCON<6>)).

31.3.14 Channel Event Transfer Termination
Channel transfer is terminated in any of the following cases:
• A transfer is aborted as described in 31.3.16 “Channel Abort”.
• A cell transfer (CHCSIZ bytes (DCHxCSIZ transferred)) completes.
• The DMA has transferred the larger of CHSSIZ or CHDSIZ bytes (block transfer complete),
the channel is disabled in hardware and must be re-enabled by user software before the
channel will respond to channel events.
• A pattern match occurs if enabled.
• An abort interrupt, CHAIRQ<7:0> (DCHxECON<23:16>), occurs if abort interrupts are
enabled by AIRQEN bit (DCHxECON<3>).
• An address error occurs.
An example of how to use the abort interrupt would be a transfer from a UART channel to the
memory. While the UART Receive Data Available interrupt can be used to start the transfer, the
UART Error interrupt can abort the transfer. This way, whenever an error occurs on the communication channel (a framing/parity error or even an overrun), the transfer is stopped and the user
code gets control in an ISR (if the abort interrupt is enabled for the DMA controller).
A summary of the status flags affected by channel transfer initiation or termination is provided in
Table 31-5. Channel abort events are allowed if the channel is enabled, CHEN = 1, or if the user
elects to allow events while the channel is disabled, CHAED = 1.

DS61117F-page 31-48

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
Channel Event Behavior
Event

Description and Function

Registers Affected

Events Initiating Transfers
System Interrupt Matching
CHSIRQ<7:0>(1,2)

The channel event detect will be set.

Channel Chain Event

This will enable the channel if not already set. If an event detect CHEN = 1
is pending, a channel transfer will begin immediately.

User Writes the CFORCE bit(1) The channel event detect will be set.

CHEDET = 1

CHEDET = 1

Events Terminating Transfers
System Interrupt Matching
CHAIRQ<7:0>(1,2)

The channel event detect will be reset and the channel turned
off. The abort interrupt flag is set.

CHEDET = 0
CHEN = 0
CHAIF = 1

Pattern Match(1)

This occurs when any byte of data written in a transaction
matches the data in CHPDAT.
The channel event detect is reset.
The channel is turned off if CHAEN = 0. This event is treated
as a completed block transfer.
Pointers are reset.

CHEDET = 0
CHEN = 0
CHBCIF = 1
CHSPTR = 0
CHDPTR = 0
CHCPTR = 0

Cell Transfer is Complete

This occurs when CHCSIZ bytes have been transferred. The
CHEDET = 0
transfer event detect is reset and the channel remains enabled CHCCIF = 1
pending the next event.

Block Transfer is Complete

The channel event detect is reset.
The channel is turned off if CHAEN = 0. This event is treated
as a completed transfer.
Pointers are reset.

User Writes the CABORT bit

The channel is turned off and the channel event detect is reset. CHEDET = 0
The pointers are reset.
CHEN = 0
CHSPTR = 0
CHDPTR = 0
CHCPTR = 0

Address Error is Detected

The channel is turned off and the event detect is reset. The
address error interrupt flag is set.

Note 1:
2:

CHEDET = 0
CHEN = 0
CHBCIF = 1
CHSPTR = 0
CHDPTR = 0
CHCPTR = 0

CHEDET = 0
CHEN = 0
CHERIF = 1

Events are allowed only when the channel is enabled, or the user allows events while disabled (CHEN = 1
or CHAED = 1).
The DMA Controller maintains its own flags for detecting start and abort interrupt requests (IRQs) in the system, and is completely independent of the INT Controller IES/IFS flags. Once the start or abort IRQ system
events are triggered, they will be detected automatically by the DMA controller internal logic, without the
need for user intervention.

© 2010 Microchip Technology Inc.

DS61117F-page 31-49

DMA Controller

Table 31-5:

31

PIC32MX Family Reference Manual
31.3.15 Channel Abort Interrupt
A channel can elect to abort a cell transfer if an interrupt event occurs. The interrupt is selected
by the channel’s abort IRQ, CHAIRQ<7:0> (DCHxECON<23:16>). Any one of the device
interrupt events can cause a channel abort. An abort only occurs if enabled by AIRQEN bit
(DCHxECON<3>).
If this occurs (often a timer time-out or a module error flag), the channel’s status flags will
indicate the external abort event on the channel in question by setting its CHTAIF bit
(DCHxINT<1>). The Source and Destination Pointers are not reset, allowing the user to recover
from the error.

31.3.16 Channel Abort
A channel transfer can be aborted by the user by writing the CABORT bit (DCHxECON<6>).
When a transfer is aborted, the current bus transaction will be completed and any transactions
that remain will be aborted. The CHEN bit (DCHxCON<7>) will be cleared. When the user
writes the CABORT bit, the Source and Destination Pointers are reset.

31.3.17 Address Error
If the address (either source or destination) occurring during a transfer is an illegal address, the
channel’s address error interrupt flag CHERIF bit (DCHxINT<0>) will be set. The channel will be
disabled (i.e., CHEN bit will be reset by hardware).
The channel status is unaffected to aid in the debug of the problem.

31.3.18 DMA Suspend
DMA transactions are suspended immediately if the SUSPEND bit (DMACON<12>) is set. The
current read or write will be completed. If the suspend comes during the read portion of the
transaction, the transaction will be suspended and the write will be put on hold. If the suspend
comes during the write portion of the transaction, the write will complete and the pointers
updated as normal. Any transactions that were in process will continue where they left off when
the SUSPEND bit is cleared.
Depending on the device variant, when the DMA module is suspended by setting the
SUSPEND bit, the user application should poll the DMABUSY bit (DMACON<11>) to determine
when the module is completely suspended following the completion of the current transaction.
Note:

Example 31-8:

The DMABUSY bit is not available on all device. Refer to the specific device data
sheet for availability.

DMA Controller Suspension

/*
The following code example will suspend the DMA Controller.
*/
DMACONSET=0x00001000;
// suspend the DMA controller
while(!(DMACONbits.busy)); // wait for the transfer to be actually suspended
// let the CPU have complete control of the bus
DMACONCLR=0x00001000;

// clear the suspend mode and let the DMA operate normally
// from now on, the CPU and DMA controller share the bus access

DS61117F-page 31-50

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
INTERRUPTS
The DMA device has the ability to generate interrupts reflecting the events that occur during the
channel’s data transfer:
• Error interrupts, signaled by each channel’s CHERIF bit (DCHxINT<0>) and enabled using
the CHERIE bit (DCHxINT<16>). This event occurs when there is an address error
occurred during the channel transfer operation.
• Abort interrupts, signaled by each channel’s CHTAIF bit (DCHxINT<1>) and enabled using
the CHTAIE bit (DCHxINT<17>). This event occurs when a DMA channel transfer gets
aborted because of a system event (interrupt) matching the CHAIRQ<7:0>
(DCHxECON<23:16>) when the abort interrupt request is enabled, AIRQEN = 1
(DCHxECON<3>).
• Block complete interrupts, signaled by each channel’s CHBCIF bit (DCHxINT<3>) and
enabled using the CHBCIE bit (DCHxINT<19>). This event occurs when a DMA channel
block transfer is completed.
• Cell complete interrupts, signaled by each channel’s CHCCIF bit (DCHxINT<2>) and
enabled using the CHCCIE bit (DCHxINT<18>). This event occurs when a DMA channel
cell transfer is completed.
• Source Address Pointer activity interrupts: either when the Channel Source Pointer
reached the end of the source, signaled by the CHSDIF bit (DCHxINT<7>) and enabled by
CHSDIE bit (DCHxINT<23>), or when the Channel Source Pointer reached midpoint of the
source, signaled by the CHSHIF bit (DCHxINT<6>) and enabled by the CHSHIE bit
(DCHxINT<22>).
• Destination Address Pointer activity interrupts: either when the Channel Destination Pointer
reached the end of the destination, signaled by the CHDDIF bit (DCHxINT<5>) and
enabled by the CHDDIE bit (DCHxINT<21>), or when the Channel Destination Pointer
reached midpoint of the destination, signaled by the CHDHIF bit (DCHxINT<4>) and
enabled by the CHDHIE bit (DCHxINT<20>).
All the interrupts belonging to a DMA channel map to the corresponding channel interrupt vector.
Note:

Not all DMA channels are available on all devices. Refer to the specific device data
sheet for availability.

The corresponding DMA channels interrupt flags are:
•
•
•
•
•
•
•
•

DMA0IF (IFS1<16>)
DMA1IF (IFS1<17>)
DMA2IF (IFS1<18>)
DMA3IF (IFS1<19>)
DMA4IF (IFS1<20>)
DMA5IF (IFS1<21>)
DMA6IF (IFS1<22>)
DMA7IF (IFS1<23>)

All of these interrupt flags must be cleared in software.
A DMA channel is enabled as a source of interrupts through the respective DMA interrupt enable
bits:
•
•
•
•
•
•
•
•
•
•

DMA0IE (IEC1<17>)
DMA1IE (IEC1<18>)
DMA2IE (IEC1<19>)
DMA3IE (IEC1<20>)
DMA0IE (IEC1<16>)
DMA1IE (IEC1<17>)
DMA2IE (IEC1<18>)
DMA3IE (IEC1<19>)
DMA4IE (IEC1<20>)
DMA5IE (IEC1<21>)

© 2010 Microchip Technology Inc.

DS61117F-page 31-51

DMA Controller

31.4

31

PIC32MX Family Reference Manual
•
•
•
•
•
•

DMA6IE (IEC1<22>)
DMA7IE (IEC1<23>)
DMA4IE (IEC1<20>)
DMA5IE (IEC1<21>)
DMA6IE (IEC1<22>)
DMA7IE (IEC1<23>)

The interrupt-priority-level bits and interrupt-subpriority-level bits must also be configured:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•

DMA0IP<2:0> (IPC9<12:10>), DMA0IS<1:0> (IPC9<9:8>).
DMA1IP<2:0> (IPC9<20:18>), DMA1IS<1:0> (IPC9<17:16>).
DMA2IP<2:0> (IPC9<28:26>), DMA2IS<1:0> (IPC9<25:24>).
DMA3IP<2:0> (IPC10<4:2>), DMA3IS<1:0> (IPC10<1:0>).
DMA0IP<2:0> (IPC9<4:2>), DMA0IS<1:0> (IPC9<1:0>)
DMA1IP<2:0> (IPC9<12:10>), DMA1IS<1:0> (IPC9<9:8>)
DMA2IP<2:0> (IPC9<20:18>), DMA2IS<1:0> (IPC9<17:16>)
DMA3IP<2:0> (IPC9<28:26>), DMA3IS<1:0> (IPC9<25:24>)
DMA4IP<2:0> (IPC10<4:2>), DMA4IS<1:0> (IPC10<1:0>)
DMA5IP<2:0> (IPC10<12:10>), DMA5IS<1:0> (IPC10<9:8>)
DMA7IP<2:0> (IPC10<20:18>), DMA6IS<1:0> (IPC10<17:16>)
DMA7IP<2:0> (IPC10<28:26>), DMA7IS<1:0> (IPC10<25:24>)
DMA4IP<2:0> (IPC10<4:2>), DMA0IS<1:0> (IPC10<1:0>).
DMA5IP<2:0> (IPC10<12:10>), DMA1IS<1:0> (IPC10<9:8>).
DMA6IP<2:0> (IPC10<20:18>), DMA2IS<1:0> (IPC10<17:16>).
DMA7IP<2:0> (IPC10<28:26>), DMA3IS<1:0> (IPC10<25:24>).

31.4.1

Interrupt Configuration

Each DMA channel internally has multiple interrupt flags (CHSDIF, CHSHIF, CHDDIF, CHDHIF,
CHBCIF, CHCCIF, CHTAIF, CHERIF) and corresponding enable interrupt control bits (CHSDIE,
CHSHIE, CHDDIE, CHDHIE, CHBCIE, CHCCIE, CHTAIE, CHERIE).
However, for the interrupt controller, there is just one dedicated interrupt flag bit per channel,
DMAxIF, DMA4IF, DMA5IF, DMA6IF, DMA7IF(IFS1<20:17>) and the corresponding interrupt
enable/mask bits, DMAxIE(IEC1<23:16>).
Note:

Depending on the device variant, up to 8 (i.e., 0-7) interrupt flags and interrupt
enable/mask bits are available. Refer to the specific device data sheet for
availability.

Therefore, note that all of the interrupt conditions for a specific DMA channel share just one
interrupt vector. Each DMA channel can have its own priority level independent of other DMA
channels.
Note that the DMAxIF bits will be set without regard to the state of the corresponding enable bits
DMAxIE. The DMAxIF bits can be polled by software if desired.
The DMAxIE bits are used to define the behavior of the Vector Interrupt Controller or INT when
a corresponding DMAxIF bit is set. When the corresponding DMAxIE bit is clear, the INT module
does not generate a CPU interrupt for the event. If the DMAxIE bit is set, the INT module will
generate an interrupt to the CPU when the corresponding DMAxIF bit is set (subject to the priority
and subpriority as follows).
It is the responsibility of the user’s software routine that services a particular interrupt to clear the
appropriate interrupt flag bit before the service routine is complete.
The priority of each DMA channel can be set independently with the DMAxIP bits in the IPCx
register. These priorities define the priority group to which the interrupt source will be assigned.
The priority groups range from a value of 7 (the highest priority), to a value of 0, which does not
generate an interrupt. An interrupt being serviced will be preempted by an interrupt in a higher
priority group.

DS61117F-page 31-52

© 2010 Microchip Technology Inc.

Section 31. DMA Controller

The priority group and subpriority bits allow more than one interrupt source to share the same
priority and subpriority. If simultaneous interrupts occur in this configuration, the natural order of
the interrupt sources within a Priority/subpriority group pair determine the interrupt generated.
The natural priority is based on the vector numbers of the interrupt sources. The lower the vector
number the higher the natural priority of the interrupt. Any interrupts that were overridden by
natural order will then generate their respective interrupts based on Priority, subpriority and
natural order after the interrupt flag for the current interrupt is cleared.
After an enabled interrupt is generated, the CPU will jump to the vector assigned to that interrupt.
The vector number for the interrupt is the same as the natural order number. The CPU will then
begin executing code at the vector address. The user’s code at this vector address should
perform any application-specific operations and clear the DMAxIF interrupt flags, and then exit.
Refer to the vector address table details in Section 8. “Interrupts” (DS61108) in the “PIC32MX
Family Reference Manual” for more information on interrupts.
Table 31-6:

DMA Interrupt Vectors for Various Offsets with EBASE = 0x8000:0000

Interrupt

Vector/Natural
Order

IRQ
Number

Vector
Address
IntCtl.VS
= 0x01

Vector
Address
IntCtl.VS
= 0x02

Vector
Address
IntCtl.VS
= 0x04

Vector
Address
IntCtl.VS
= 0x08

Vector
Address
IntCtl.VS
= 0x10

DMA0

37

49

8000 06A0

8000 0B40

8000 1480

8000 2700

8000 4C00

DMA1

38

50

8000 06C0

8000 0B80

8000 1500

8000 2800

8000 4E00

DMA2

39

51

8000 06E0

8000 0BC0

8000 1580

8000 2900

8000 5000

DMA3

40

52

8000 0700

8000 0C00

8000 1600

8000 2A00

8000 5200

DMA0

36

48

8000 0680

8000 0B00

8000 1400

8000 2600

8000 4A00

DMA1

37

49

8000 06A0

8000 0B40

8000 1480

8000 2700

8000 4C00

DMA2

38

50

8000 06C0

8000 0B80

8000 1500

8000 2800

8000 4E00

DMA3

39

51

8000 06E0

8000 0BC0

8000 1580

8000 2900

8000 5000

(1)

40

52

8000 0700

8000 0C00

8000 1600

8000 2A00

8000 5200

DMA5(1)

41

53

8000 0720

8000 0C40

8000 1680

8000 2B00

8000 5400

DMA6(1)

42

54

8000 0740

8000 0C80

8000 1700

8000 2C00

8000 5600

DMA7(1)

43

55

8000 0760

8000 0CC0

8000 1780

8000 2D00

8000 5800

DMA4

40

52

8000 0700

8000 0C00

8000 1600

8000 2A00

8000 5200

DMA4

DMA5

41

53

8000 0720

8000 0C40

8000 1680

8000 2B00

8000 5400

DMA6

42

54

8000 0740

8000 0C80

8000 1700

8000 2C00

8000 5600

DMA7

43

55

8000 0760

8000 0CC0

8000 1780

8000 2D00

8000 5800

Note 1:

These interrupts are not available on all devices. Refer to the specific device data sheet for availability.

© 2010 Microchip Technology Inc.

DS61117F-page 31-53

DMA Controller

The subpriority bits allow setting the priority of an interrupt source within a priority group. The values of the subpriority range from 3 (the highest priority), to 0 the lowest priority. An interrupt with
the same priority group but having a higher subpriority value will not preempt a lower subpriority
interrupt that is in progress.

31

PIC32MX Family Reference Manual
Example 31-9:

DMA Channel Initialization with Interrupts Enabled Code Example

/*
The following code example illustrates a DMA channel 0 interrupt configuration.
When the DMA channel 0 interrupt is generated, the CPU will jump to the vector assigned to
DMA0 interrupt.
*/
IEC1CLR=0x00020000;
IFS1CLR=0x00020000;
IEC1CLR=0x00010000;
IFS1CLR=0x00010000;

//
//
//
//

DMACONSET=0x00008000;
DCH0CON=0x03;

// enable the DMA controller
// channel off, priority 3, no chaining

DCH0ECON=0;

// no start or stop irq’s, no pattern match

DCH0SSA=0x1d010000;
DCH0DSA=0x1d020000;
DCH0SSIZ=200;
DCH0DSIZ=200;
DCH0CSIZ=200;

//
//
//
//
//
//

DCH0INTCLR=0x00ff00ff;
DCH0INTSET=0x00090000;

// clear existing events, disable all interrupts
// enable Block Complete and error interrupts

IPC9CLR=0x00001f00;
IPC9SET=0x00001600;
IPC9CLR=0x0000001f;
IPC9SET=0x00000016;
IEC1SET=0x00020000;
IEC1SET=0x00010000;

//
//
//
//
//
//

DCH0CONSET=0x80;

// turn channel on
// initiate a transfer
// set CFORCE to 1

DCH0ECONSET=0x00000080;

disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag
disable DMA channel 0 interrupts
clear any existing DMA channel 0 interrupt flag

program the transfer
transfer source physical address
transfer destination physical address
source size 200 bytes
destination size 200 bytes
200 bytes transferred per event

clear the DMA channel 0 priority and sub-priority
set IPL 5, sub-priority 2
clear the DMA channel 0 priority and sub-priority
set IPL 5, sub-priority 2
enable DMA channel 0 interrupt
enable DMA channel 0 interrupt

Example 31-10: DMA Channel 0 ISR Code Example
/*
The following code example demonstrates a simple Interrupt Service Routine for DMA channel 0
interrupts. The user’s code at this vector should perform any application specific operations
and must clear the DMA0 interrupt flags before exiting.
*/
void __attribute__ ((interrupt(ipl3), at_vector(37))) __DMA0Interrupt(void)
void __ISR(_DMA_0_VECTOR, ipl5) __DMA0Interrupt(void)
{
int dmaFlags=DCH0INT&0xff;
// read the interrupt flags
/*
perform application specific operations in response to any interrupt flag set
*/
DCH0INTCLR=0x000000ff;
//
IFS1CLR = 0x00020000;
//
IFS1CLR = 0x00010000;
// Be sure
//
}

Note:

DS61117F-page 31-54

clear the DMA channel interrupt flags
Be sure to clear the DMA0 interrupt flags
to clear the DMA0 interrupt flags
before exiting the service routine.

The DMA ISR code example shows MPLAB® C32 C compiler specific syntax. Refer
to your compiler manual regarding support for ISRs.

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
OPERATION IN POWER-SAVING AND DEBUG MODES
31.5.1

DMA Operation in Idle Mode

When the device enters Idle mode, the system clock sources remain functional and the DMA
module continues to operate.
On some variants, the SIDL bit (DMACON<13>) selects whether the module will stop or continue
functioning on Idle.
• If SIDL = 0, the module will continue operation in Idle mode and will have the clocks turned
off.
• If SIDL = 1, the module will discontinue operation in Idle mode. The DMA module will turn
off the clocks so that the power consumption is more efficient.
Note:

31.5.2

The DMA module cannot be used by a peripheral that has its SIDL bit set to ‘1’.

DMA Operation in Sleep Mode

When the device enters Sleep mode, the system clock is disabled. No DMA activity can occur in
this mode.

31.5.3

DMA Operation in Debug Mode

The FRZ bit (DMACON<14>) determines whether the DMA module will run or stop while the CPU
is executing debug exception code (i.e., application is halted) in Debug mode. When FRZ = 0,
the DMA module continues to run even when application is halted in Debug mode. When
FRZ = 1 and the application is halted in Debug mode, the module will freeze its operations and
make no changes to the state of the DMA module. The module will resume its operation after
CPU resumes execution.
Note:

31.6

The FRZ bit is readable and writable only when the CPU is executing in Debug
Exception mode. In all other modes, the FRZ bit reads as ‘0’. If the FRZ bit is
changed during Debug mode, the new value does not take effect until the current
Debug Exception mode is exited and re-entered. During the Debug Exception
mode, the FRZ bit reads the state of the peripheral when entering Debug mode.

EFFECTS OF VARIOUS RESETS
31.6.1

Device Reset

All DMA registers are forced to their reset states upon a device Reset. When the asynchronous
Reset input goes active, the DMA logic:
• Resets all fields in DMACON, DMASTAT, DMAADDR, DCRCCON, DCRCDATA and
DCRCXOR
• Sets the appropriate values in each channel’s register fields: DCHxCON, DCHxECON,
DCHxINT, DCHxSSIZ, DCHxDSIZ, DCHxSPTR, DCHxDPTR, DCHxCSIZ, DCHxCPTR
and DCHxDAT
• Registers DCHxSSA and DCHxDSA have random values after a reset
• Aborts any ongoing data transfers

31.6.2

Power-on Reset

All DMA registers are forced to their reset states upon a Power-on Reset.

31.6.3

Watchdog Timer Reset

All DMA registers are forced to their reset states upon a Watchdog Timer Reset.

© 2010 Microchip Technology Inc.

DS61117F-page 31-55

DMA Controller

31.5

31

PIC32MX Family Reference Manual
31.7

RELATED APPLICATION NOTES
This section lists application notes that are related to this section of the manual. These
application notes may not be written specifically for the PIC32MX device family, but the concepts
are pertinent and could be used DMA Controller with modification and possible limitations. The
current application notes related to the Direct Memory Access (DMA) module are:
Title

Application Note #

No related application notes at this time
Note:

DS61117F-page 31-56

N/A

Visit the Microchip web site (www.microchip.com) for additional application notes
and code examples for the PIC32MX family of devices.

© 2010 Microchip Technology Inc.

Section 31. DMA Controller
REVISION HISTORY

DMA Controller

31.8

Revision A (October 2007)
This is the initial released version of this document.

Revision B (October 2007)
Updated document to remove Confidential status.

Revision C (April 2008)
Revised status to Preliminary; Revised U-0 to r-x; Revised Table 31-1; Revised Table 31-2
(DCHxCON, bit 3), deleted Note 1; Revised Registers 31-19, 31-39, 31-43, 31-47, 31-48, 31-49,
31-53; Revise Sections 31.3, 31.3.2; Revised Examples 31-1, 31-3, 31-4, 31-6, 31-7, 31-8;
Delete Example 31-2 and renumber examples; Delete Section 31.3.3 and renumber sections;
Revised Section 31.3.20.7.

Revision D (June 2008)
Revised Registers 31-58 to 31-60, Footnote; Revised Example 31-8; Change Reserved bits
“Maintain as” to “Write”; Added Note to ON bit (DMACON Register).

Revision E (August 2009)
This revision introduces new bits and functionality that are only available on certain devices. The
following details the resulting changes:
• DMA Register Summary (Table 31-1)
- Added the BUSY, BYTO1, BYTO0, WBO, BITO, CRCTYP and CHBUSY bits
- Removed references to the IEC1, IPC9 and IFS1 registers
- Added the Address Offset column to the DMA Register Summary
- Added Notes 1, 2 and 3, which describe the Clear, Set and Invert registers
- Added Notes 4 and 5 regarding the availability of certain bits and ranges of bits
depending on the device variant
• Added Notes describing the Clear, Set and Invert registers to the following registers:
- DMACON (Register 31-1)
- DMASTAT (Register 31-2)
- DMAADDR (Register 31-3)
- DCRCCON (Register 31-4)
- DCRCDATA (Register 31-5)
- DCRCXOR (Register 31-6)
- DCHxCON (Register 31-7)
- DCHxECON (Register 31-8)
- DCHxINT (Register 31-9)
- DCHxSSA (Register 31-10)
- DCHxDSA (Register 31-11)
- DCHxSSIZ (Register 31-12)
- DCHxDSIZ (Register 31-13)
- DCHSPTR (Register 31-14)
- DCHxDPTR (Register 31-15)
- DCHxCSIZ (Register 31-16)
- DCHxCPTR (Register 31-17)
- DCHxDAT (Register 31-18)
• Removed these registers: IFS1, IEC1 and IPC9
• Added the BUSY bit (DMACON<11>) and Note 1 regarding availability of the SIDL and
BUSY bits to Register 31-1

© 2010 Microchip Technology Inc.

31

DS61117F-page 31-57

PIC32MX Family Reference Manual
Revision E (August 2009) (Continued)
• Updated the DMACH bit (DMASTAT<2:0>) and added Note 2 regarding the availability of
all bits in Register 31-2
• Added the BYTO1, BYTO0, WBO, BITO and CRCTYP bits, updated bits PLEN<4:0> and
CRCCH<2:0>, and added Notes 1 and 2 to Register 31-4
• Updated DCRCDATA bits and added Note 1 to Register 31-5
• Updated DCRCXOR bits and added Note 1 to Register 31-6
• Added CHBUSY bit (DCHxCON<15>) and added Note 1 to Register 31-7
• Updated DCHxSSIZ bits and added Note 1 to Register 31-12
• Updated DCHxDSIZ bits and added Note 1 to Register 31-13
• Updated DCHxSPTR bits and added Note 2 to Register 31-14
• Updated DCHxDPTR bits and added Note 1 to Register 31-15
• Updated DCHxCSIZ bits and added Note 1 to Register 31-16
• Updated DCHxCPTR bits and added Note 2 to Register 31-17
• Updated the lowest priority channel number and added a related note to the fourth
paragraph in 31.3.3 “Channel Chaining Mode”
• Added information on suspending the DMA module and a related Note to
31.3.6 “Suspending Transfers” and 31.3.18 “DMA Suspend”
• Updated 31.3.5 “Special Function Module (SFM) Mode” to differentiate between the
16-bit and 32-bit CRC
• Added 31.3.5.5 “Calculating the IP Header Checksum”
• Added DMA channel interrupt flags, enable bits and priority-level bits to 31.4 “Interrupts”
• Added DMA interrupt vectors (DMA4-DMA7) to Table 31-6
• Updated 31.5.1 “DMA Operation in Idle Mode”

Revision F (October 2010)
This revision includes the following updates:
• Added a note at the beginning of this section, which provides information on complementary
documentation
• Changed all occurrences of “Reserved: Write ‘0’; ignore read” to “Unimplemented: Read
as ‘0’, and updated the default POR definitions in all registers
• Added Notes 1, 2 and 3, which describe the Clear, Set and Invert registers to the following:
- Table 31-1: DMA Register Summary
- Register 31-1: DMACON: DMA Controller Control Register(1,2,3)
- Register 31-4: DCRCCON: DMA CRC Control Register(1,2,3)
- Register 31-5: DCRCDATA: DMA CRC Data Register(1,2,3)
- Register 31-6: DCRCXOR: DMA CRCXOR Enable Register(1,2,3)
- Register 31-7: DCHxCON: DMA Channel x Control Register(1,2,3)
- Register 31-8: DCHxECON: DMA Channel x Event Control Register(1,2,3)
- Register 31-9: DCHxINT: DMA Channel x Interrupt Control Register(1,2,3)
- Register 31-10: DCHxSSA: DMA Channel x Source Start Address Register(1,2,3)
- Register 31-12: DCHxSSIZ: DMA Channel x Source Size Register(1,2,3)
- Register 31-13: DCHxDSIZ: DMA Channel x Destination Size Register(1,2,3)
- Register 31-16: DCHxCSIZ: DMA Channel x Cell-Size Register(1,2,3)
- Register 31-18: DCHxECON: DMA Channel x Event Control Register(1,2,3)
• Removed all Clear, Set and Invert registers
• Removed all Interrupt registers
• Changed the name of the BUSY bit to DMABUSY in Register 31-1 and in Table 31-1
• Added a note box just after the last paragraph of 31.3.5 “Special Function Module (SFM)
Mode”
• Minor formatting and text updates have been incorporated throughout the document

DS61117F-page 31-58

© 2010 Microchip Technology Inc.

Note the following details of the code protection feature on Microchip devices:
•

Microchip products meet the specification contained in their particular Microchip Data Sheet.

•

Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.

•

There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

•

Microchip is willing to work with the customer who is concerned about the integrity of their code.

•

Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
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Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
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Information contained in this publication regarding device
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© 2010, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
ISBN: 978-1-60932-621-0
Microchip received ISO/TS-16949:2002 certification for its worldwide
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© 2010 Microchip Technology Inc.

DS61117F-page 59

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