Cipher_Tape Cipher Tape

User Manual: Cipher_Tape

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S•• IOU . , Section.

I . . 100 . , '.ction.

-119 ••

•
f

CIPHER DATA
. STREAMING TAPE
TRANSPORT

L~_5_3 S 5 j
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£0{/,52-

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Tope Speed

100 ips, SO ips (3200 bpi only), 25 ips

Low-Speed Variations (LSV)

%1% of nominal

Ins1an1oneous Speed Variation (lSV)

:4% of long-1erm speed

Write Skew

300 microinches, maximum

Rew i rd Speed

175 ips, overage (10 112 -inch reel)

Nominal Access Time (ms)

25 ips

100 ips

SO ips

Read

260

120

Write

260

120

Redd

120

780

350

Write

120

780

350

Read

Write

1600 bpi

40,000

160,000

N/A

3200 bpi

N/A

160,000

Nominal Reposiiion Time (ms)

Nominal Reins1ruct Time (ms)

Character Rate (Hz)

1600 bpi (pE) or 3200 bpi

Data Density
Tape (Comp.J1er grade)

ANSI X3.40-1976

Width

0.5 inch

Thickness

105 mil

Reel Size
Tape Tension
Net V:eight
Shipping VJeight

10 '/2. inches max.
7 inches min.

7 oz., nomi nat
80 pounds (36.0 kg)
98 pounds (44.5 kg)

Table I-I. fl~echGn icaJ and Electrical S;>ecifications

Dimensions
Height

8.75 inches (22.2 cm)

Width

17.0 inches (43.2 em)

Depth (from
mounting surface)

22.0 inches (55.9 cm)

Mount ing (standard 19-inch
RETMA rack; slide
mounting provided)

EIA Specifications

100, 120, 220, 240 Vae (+10%, -15%); 230

Power

Vac (:!:IO%) 48 - 61 Hz; 270 watts, max.

Data Reliability:
Write (certified tape)

1 error in 10 8 bytes

Read Recoverable

I error in 109 bytes

Read Perrnment

I error in 10 10 bytes

Operating Temperature
Relative Humidity

13-40 degrees Centigrade

20-85% noncondensing
7,500 feet (10,000 feet optional)

Altitude
Interface Impedance,

130 ohms at 3 Vdc

Sink Current

25 rna, max.
0.4 Vde, max.

Logic Low

2.4 Vdc, min.

Logic Hig,
Rise/Fall Time
Daisy-Chain Capabilities

Cable Characteristics
MTBF

MTTR

100 nanoseconds, max.
Eight dual-speed tape drives or four dualspeed tope drives plus one formatted drive,
25 feef maximum 10tal if active repeaters
nof used.
28 AWG fiat ribbon, 22 or 24 AWG twisted
pair.
5500 hours

30 minutes (to isolate and replace major
subassemblies)
Table I-I. fliechanicaJ and Electrical Specifications (Continued)

4-5

INTRODUCTION TO STREAMING TAPE OPERATION

Streaming tape operation is simply writing data to tape without stopping and starting
between each record block. Interblock gaps, as required in the ANSI format, are inserted
automatically "on the fly". This concept, although not new, was focused on in IBM's
Model 8809 in late 1978. All tape drives currently being manufactured have the
capability of streaming.
So what is so special about the Cipher Model F880 Microstreamer? It is manufactured
specifically for streaming tape operation under a design concept in which a severe design
constraint, that of start/stop time, has been greatly relaxed. As shown in Figure 5, a
typical 125 ips, vacuum column tape drive is capable of starting and stopping in 3.5
milliseconds, within the G.6-inch inter-record gap, while the Microstreamer takes up to
24-0 milliseconds to ramp up to a speed of 100 ips.
•
Obviously, the streaming tape drive does not generate standard interblock gaps in the
usual manner, with its 24-0-millisecond ramp-up time (at 100 ips). The manner in which
the Microstreamer generates the standard interblock gap is explained on page 8 in the
Repositioning section.
The relaxation of the previously vital tape-access time constraint has made possible
numerous design changes:
o

Capstan servo is no longer required.

Reel servos are simpIlfied.

Lower power and less expensive motors are required.

Tape is loaded and unloaded automatically.

Less expensive tape buffering is required.

START/STOP
125 IPS
STREAMING DRIVE

100 IPS

3.5

240

Figure 5. Tape Access Time
6

TAPE CLEANER
@TAPE ROLLER GUIDE (3)

o ROLLER
COMPLIANCE ARM
GUIDE

Figure 1. Tape P:Jth

LJ-5

BACKUP TIME FOR VARIOUS DISK CAPACITIES

The total time rectuired for the aperator to complete the task of backup for a given disk
capacity is given in Tables 8 and 9. These calculations are based on a write speed of 100
ips and a rewind speed of 200 ips. Additionally, 1 minute is added for each tape load
function.
I

BLOCK SIZE IN BYTES
2048 /
1024
4096

512

4.4-

5.3

7.4

10.7

8.0

9.0

10.7

13.9

21.3

36.0

12.3

13.1

16.4

21.3

31 .. 9

54,,1

·15.6

18.0

21.3

28.7

4-3 .. 5

72.2

100

19.7

22.1

27.1

36.0

54.1

89.4-

160

32.0

35.3

4-2~6

56 .. 6

86.1

14-4.3

200

4-0.2

44.3

53.3

71.3

108.2

179.5

DISK SIZE
MBYTES

8192

3.9

·256

18.0

Table 8. Time in Minutes for Various Capacity and Block Size at 1600 bpi

BLOCK SIZE IN BYTES
1024
2048

DISK SIZE
MBYTES

8192

4096

2.. 5

2.5

3.3

4.1

4.9

6.6

512

256

4.9

9.0

16.6

7.4

10.7

17.2

31.2

8 .. 2

10.7

15.6

25.4

46.7

8.2

10.7

13.9

20.5

34.4

62.3

100

11.5

13.3

18.0

26.2

43.5

77.9

160

18,,0

2L3

28,,7

4L8

69,,7

124.6

200

22.1

26.2

35.2

53.3

86.1

155.8

Tabie 9. Time in Minutes for Various Capacity and Siock Size at 3200 bpi

y-~

"'~bles 10 and 11 show the number of 10.5-inch reels of 1.5-mil. (standard 2400-foot) tape
!:cquired to back up a specific disk size. The figures shown include all formatting
characters and record gaps.

DISK SIZE
MBYTES

8192

4096

0.48

0.54

0.65

0.97

1.1

1.50

BLOCK SIZE IN BYTES
2048
1024

512

256

0.9

1.3

2~2

1.30

1.7

2.6

4.4

1.6

2.00

2.6

3.9

6.6

1.90

2.2

2.60

3.5

5.3

8.8

100

2.40

2.7

3.30

4.4

6.6

10.9

160

3.90

4.3

5 .. 20

6.9

10 .. 5

17.6

200

4.90

5.4

6.50

8.7

13.2

21.9

Table 10.

Number of Reels of Tape for Various Capacity and Block Size at 1600 bpi
(2400' Reel)

DISK SIZE
MBYTES

8192

4096

BLOCK SIZE IN BYTES
2048
1024

0.3

0.4

0.5

0.6

0.8

512

256

0.6

1.1

1.9

0.9

1.3

2.1

3.8

1.0

1.3

1.9

3.1

5.7

1.0

1.3

1.7

2.5

4.2

7.6

100

1.4

1.6

2.2

3.2

5.3

9.5

160

2.2

2.6

~.5

5.1

8.5

15.2

200

2.7

3.2

403

6.5

10.5

19,,0

Table 11.

Number of Reels of Tape for Various Capacity and Block Size at 3200 bpi
(2400' Reel)

'-/-7

TAPE CAPACITY

The total number of bytes to be stored in a single reel of tape varies with the block size.
Figure 29 gives an idea of the capacity achievable for various block lengths. The chart
allows for a standard gap size of 0.6 inch and takes into account the preamble and
postamble characters required for each block of data recorded in PE format.

CIPHER DATA PRODUCTS
MICROSTREAMER F8aO
STORAGE CAPACITY 10%" TAPE REEL

-70- -

.- -

-- --- -- -

--=...;;;:-----.,

3200 BPI

en
w

I-

>
CD

«
(!)

60
8K
BLOCKS
50

>
IU
e:(

a..

«
CJ
w

-301K
{
BLOCK· _ _

(!)

0
Ien

«
a:::

1600 BPI

40-

BLOCK SIZE IN THOUSANDS' BYTES

Figure 29. Storage Capacity vs Block Size

FLASH FRONT PANEL
LOAD LIGHT

FLASH fRONT PANEL
UNLOAD LIGHT

SET UP TACH
fOR SHEeTED SPEED
NOUS
A. IIIEw lou .. MI'lIlacl ..1I , ..... _la .....

I. IIIWU loo.alA'III,,, '.1111 OA .".. Ia"h !un'.ldl.

o. tlIP'"d." I. 'IP' 'OIlIl~II.lIlnap",. IN. hi .....
fI.pu"uDn lI.h.. I .... 'utl"l '''I11III COlRmtntl.

Figure 2-45. On Line Sequence

~ROCESS COMMANO

OECOOE COMMANO
AND
JUMP TO COMMAND PROCESSING
SEARCH I:ORWARD FILE WITH DATA

r SEARCH REVERSE FILE WITH DATA

SEARCH FORWARD FILE

r READ REVERSE/EDIT I
I

WRITE FMK

I
I·

WRITE BLOCK/EDIT

I ERASE FIXED LENGTH GAP

READ FORWARD

SPACE REVERSE

SPACE FORWARD

SECURITY ERASE

I ERASE VARIABl.E LENGTH GAP I
Figure 2-1.6. Process Command Sequence

-C

-o

SEARCH REVERSE FILE

DIRECTION OF
POLARIZATION CHANGES
EVERY DATA TIME

POLARIZED
TAPE

DIRECTION OF POLARIZATION
.__-- CHANGES AT PHASE TIME
BETWEEN BITS OF SAME TYPE

WRITE
CURRENT

I I
SI
I
_I

READ
CURRENT
DATA BIT
STORED
ON TAPE

DATA TIME

PHASE TIME

Figure 2-1. Phose-Encoded Tope Magnetization

Tape shown with oxide side down. RNI head
on same side as oxide.

14 FT
--.

I·

END OF TAPE MARKER
(EDT)

!-3IN. MIN.

SFT
.

10 FT. MIN'
~_--tII-+-1.7 IN.

MIN.

a~------~I---------~·----------~------------~'-

~
2

I .:

1---,------

IUUIKIIIaIIIIUlII

L-____

-J==~~

__________

FILE MARK CODE
ZONE 3 ERASED
~~ZONE 2 ALL·ZEROS OURST
~
ZONE 1 ERASED OR ALL
ZEROS BURST

D[
'-

-C.

0>
Ol
0
I

40 ALL·ZERO
BYTES
1 ALL·ONES
BYTE

..,

DATA

3
1

IDENTIFICATION BURST.
THE TRAILING EDGE (LEFT)
MUST NOT OCCUR BEFORE
THE TRAILING END OF THE
BOT MARKER.

BEGINNING OF TAPE MARKER
(OOT)

FILE MARK

1
2

. 4

RECORDING AREA ----:

I~
\

1 ALL·ONES
BYTE

..,

PREAMBLE

POSTAMBLE

Figure 2-2. Nine-track PE Data Format

40 ALL·ZERO
BYTES

STREAIIIING-TAPE OPERATION
2-10. Streaming-tape operation is simply writing data to tape without stopping and
starting between each record block. Interblock gaps, as required in the ANSI format,
are inserted automatically "on the fly". Figure 2-3 illustrates in the simplest form
what a streaming drive will automatically perform if for any reason the unit must
start and stop after each block. As can be seen in the diagram, there is a period of
time called Command Reinstruct Time. This is the time after reading or writing the
lost character of the last block in which the system must instruct the tape drive to
continue or after reaching point B, the tape drive will enter what is known as a
reposition ing cycle. If the command to continue reading or writing is not received by
the time normal forward velocity reaches point B, the drive automatically
decelerates, coming to rest at point E. This sequence is called repositioning. After
coming to rest at point E, the unit waits for the next command to read or write. The
time from point E to point F is defined as access time. This repositioning and access
time may be thought of as latency time which will vary ciepending upon when the next
command is issued with respect to the last read or write character. Each leg at 100
ips takes about 240 ms, B-C = 240 ms, D-E = 240 ms. Total repositioning plus access
time equals 1025 ms at 100 ips and 150 ms at 25 ips.

BLOCK

INTER BLOCK GAP
(IBG)

BLOCK

~~~~~~3CT ILjL ~~;I

TIME

BYTE

NORMAL
A
B
F
FORWARD _ _ _043>>-~
• .'_ _ _ _ _ _....;J""III!<:~..;.f_~~.
VELOCITY
••••

•••••

...... ."

....
••
..
...,..

•••••

ACCELERATE
FORWARD

......

DECELERATE' "
FORWARD

...... ,

E ••

"'- ......

......
./

......

....... ~

DECELERATE
REVERSE

......

, .......

ACCELERATE
//
REVERSE
./

,./¥
,./

.......

,./

.......

'--

----...."",

_ _ _ REPOSITIONING TIME
•••••••• ACCESS TI ME

Figure 2-3. Repositioning Cycle
aaC-i52

'-/ ... 18

forward direction than in the reverse direction and sliqhtly more time is required to
accelerate in the reverse direction than in the forwa-rd direction. This causes the
graph to become distorted, as shown in Figure 2-4 E.

2-14.
0 allow for minor variations in acceleration and deceleration rates, the tape
is allowed to run at speed for short distances during repositioning. This provides an
offset, which is shown as points (" and C' in Figures 2-4 D and E. After repositioning,
the record head might be left several data blocks in front of the point at which the
next write or read operation is to take place. If one command is followed by another
in the opposite direction, it becomes necessary to perform an additional repositioning
to allow the required distance for tape acceleration, as illustrated in Figure 2-5. This
illustration represents a reverse read following a write forward. It can be seen that
the second reposition is a retrace of the first. It is shown offset in time for clarity
only. The double repositioning can be partially prevented if the new command is
issued somewhere along segments AB or Be, in which case that segment will be
completed and the command executed in the normal manner" If point C has been
reached, however, the entire repositioning must be completed. Repositioning may be
required when a high-speed operation follows a low-speed operation, even if they are
of the same category and in the same direction and the new command is issued within
the reinstruct time. This is necessary to allow the tape ample time to accelerate to
record speed. Figure 2:-6 illustrates this and represents a high-speed space file
forward following a low-speed read. Repositioning will also occur at other times, for
example, prior to rewinding.

REPOSITIONING

-I

Figure 2-4Ae Ramp Down (FWD)

S20-153

4-1,-/

HEAD

EOT
DIRECTION

~~~====D=A=TA=B=L=O=CK==~I~~-

~"I---

BOT

I
I
I
- - - I.... TIME
V=o------~~---------------------------TAPE
VELOCITY

Figure 2-48. Ramp Up (REV)

I
I

EaT

DIRECTION

HEAD

BOT

<4~~~------~----------~--t:~I=D=A=T=A~~~~~B=LO=C=K~~~----------------------~IC=l====~w~D~====~--

I 30 MS
- - - - 5 .~.

TIME

I
I

..,

(25 IPS)' 240 MS (100 IPS)

I
I

V = 0 ------r--------Io---~~----

(REV)
~
TAPE
VELOCITY
Figure 2-4C. Ramp Down (REV)
880-155

eaT

BOT

B
V=Q - -

Figure 2-4D. Composite Ramps at 100 ips

BOT

EOT

B
V=o - -

880-157

EOT

880-158

Figure 2-4E. Composite Ramps at 25 ips

BOT

Figure 2-5. Reverse IJirection Repositioning

L/- r~

V ~ HI - - - - -

j---'

I DATAl

- - - ' BOT'

Va LO

...

----

DIER. This signal is pulsed when the record being written/read contains an uncorrectable
error. The line goes low when an error is detected before lOSSY goes false. Error
conditions asserting this line include the following:
a.

Mutiple-track dropout: Two or more tracks have analog envelopes dropping
below the operating threshold before passing through the postamble. This is
the most common type of hard error and can be distinguished from the
others since it always occurs more than 25 microseconds after a correctable
error.

Uncorrectable parity error: All tracks have valid envelopes, but the parity is
even and the postamble has not yet been detected. This error can be
detected by the absence of ICER while IHER is set, together with parity
error on the transmitted data. An ICER may occur later, since the
postamble is unlikely to be detected. This error can be caused by writing of
incorrect parity when the external write parity option is selected. It may
also indicate excessive write-to-read crosstalk or high noise between chassis
and signal ground (if local grounding wire inside the transport is removed).

Non-O character in postamble:
The only allowable character in the
postamble is a 0 (with even parity). This is checked during the first 20
postamble character intervals.

Excessive skew: This error detection is indirect. A character bit will be
lost, causing an unavoidable postamble detection failure and a consequent
parity error when the postamble is entered.
Loss of data envelope after postamble detection: 20 character intervals
after the postamble provide time for the postamble to end and envelope
detectors to decay_ At the end of this time there must be at least eight
quiescent data channels, or an error will be reported.

leER. This signal is pulsed when a signal-track dropout is detected and error correction
is in process. This will occur before lOSSY goes false. These pulses occur throughout
the rest of the data block, and they must be latched to be sensed at the lOSSY transition.
NOTE

To ensure IBM/ANSI compatibility, the system
must rewrite records containing hard or
corrected errors on a read-after-write
verification.
IFMK. This line is pulsed on a write verification or read operation when an ISM/ANSI
compatible file mark is detected. This occurs prior to a false-going lOSSY. If a file
mark is not detected during a file mark write operation, the bad file mark should be
backspaced with a SPACE REVERSE command, and the file mark should be rewritten.
For maximum data reliability, a file mark is detected using majority logic. A file mark
is sensed when any two of the three tracks (channels 2, 6, and 7) which must be present
are present for at least 15 characters periods, and all three of the erased channels
(channel I, 3, and 4) are absent. This technique provides automatic dead track recovery
of file marks, which is essential, as error handling of file marks is notoriously poor in
most computer tape systems.

IRDY. This level indicates that tape is tensioned and is not rewinding, off line, loading,
or unloading. In the event of a hard fault shutdown, the drive goes off line and not
ready. This line should be used to precondition any tape drive command.
IONL. This level indicates that transport on-line flip-flop is set. The transport may be
placed on line during or after tape load whenever the drive was off line. This will go
false within 1 microsecond of the reception of an UNLOAD command. When IONL is
faJse, IRDY will be false.
IRYD. This level indicates that the transport is in rewind to beginning of tape
sequence. The status goes true within 1 microsecond of the REWIN 0 command and stays
true until the tape returns to BOT. IRDY is false while the drive is rewinding.

IFPT. This level indicates that the loaded reel has no write permit ring, hence the write
electronics are disabled, and write commands are prohibitedo This status goes true
during the tape-load sequence before the transport goes ready. This status is valid at all
times when tape is loaded.
.

D..DP. This level is true when the load-point reflective marker is logically at the
sensor. Since normal operation of the transport requires long ramps and repositions,
when a command is executed at BOT, the ILDP status will remain true during the
repositions. This is especially noticeable at 100 ips, when ILDP will remain true for 0.5
seconds after a command. If a REVERSE command runs into BOT, a command reset
occurs with ILDP being set. If an illegal reverse command occurs at BOT, ILDP will
remain true, but IFBY and IDBSY will sequence quickly (in less than 10 milliseconds) in
order to retain compatibility with other commands. In order to erase Model F880
interface design, ILDP goes true only at the end of a REWIND and is not set even when
crossed over physically by the transport if it is "repositioning" and is not logically at the
BOT marker.

1E0T. This level indicates that the end-of-tape marker is past the read/write head. This
signal will go false either on a rewind or by backing up over the EOT marker. This signal
should be considered ac;curate only to a few inches.
ISPEED. This signal is asserted when the transport is operating in the high-speed mode.
It is valid after 100 Y goes true for the associated command and is latched until the next
IGO command.
COMMAND DECODE

Basic transport commands are derived by decoding the REVERSE, WRITE, WRITE FILE
MARK, EDIT, and ERASE interface lines. When a command is issued to the transport
from the controller, the transport asserts the IFBY line and performs all timing and
control functions necessary for the execution of the command.
The command lines are transferred to the command registers on the trailing edge of the
IGO pulse. Any errors occurring during the execution of the command are reported to
the controller via the IHER or leER interface lines. Upon completion of the command,
the IDBSY interface line goes false, notifying the controller that it may issue another
command. All legal combinations of the interface lines are listed in Table 3. The
interface lines used for COfnmaoo decoding are defined as follows:

4-2"2

REVERSE (IREV). This is a level which, when true, specifies reverse tape
motion and when false, specifies forward tape motion.

WRITE (IWRT). This is a level which, when true, specifies the write mode of
operation and when false, specifies the read mode of operation.

WRITE FILE MARK (IWFM). This is a level which, when true and IWRT is
also true, causes a file mark to be written on the tape.

EDIT (IEDIT). When this level is true and IWRT is true, the transport
operates in the edit mode.

ERASE (IERASE). This is a level which when true in conjunction with a true
level on the IWRT line, causes the transport to execute an erase variable
length command. The transport will be conditioned to execute a normal
write command but no data will be recorded. A length of tape, as defined by
ILWD, will be erased. Alternately, if IERASE, IWRT, and IWFM command
lines are true, the transport is conditioned to execute a dummy write file
mark command. A fixed length of tape of approximately 3.75 inches will be
erased. When command lines IWRT, IWFM, IEDIT, and IERASE are true the
transport is conditioned to execute a security erase operation. A length of
tape, from the point where the command was issued to 5 feet beyond EOT,
will be erased.

IGO. This is a guIse with a minimum duration of I microsecond. The trailing edge
initiates tape motion of the selected ready transport, and latches the command into the
formatting register. The formatter address lines must be held constant from the leading
edge of IGO until IFB Y goes false.
EXTENDED INTER-RECORD GAPS. During the write operation, if successive write
commands cannot be issued within the normal reinstruct times, the Microstreamer may
be commanded to continue running forward at the selected speed and not enter a
repositioning cycle. This is accomplished by setting up the command lines for a normal
write operation and asserting and holding the IGO interface signal in the true state until
data is available at the interface. The IRG will be extended to no more than 100
inches; otherwise, the original gap will reposition automatically. If an IRG extension
must be cancelled without a new WRITE command, a NO-OP command should be placed
on the command lines before IGO is dropped. This will sequence IFBY and IDBSY but will
not generate a tape command.

A second method is available to extend the Inter-Record Gap. When switch SI-3 is in the
"ON" position, the drive will generate IRGs up to 1.2 inches in length.
(

DATA

IRG

r.- .6";.2"__---I·~1
I

The above figure shows how this option works. While streaming, if the next command is
sent between points A and B the drive will generate the standard .6-inch IRG. If the next
command is received between points Band C, the drive will begin writing the next record
shortly after the command is received, generating an IRG length between 0.6 and 1.2
inches. If the next command is received after point C, the drive will reposition, then
generate a standard 0.6-inch IRG.

The following are the basic commands that can be executed by the Model F880 tape
transport. These commands are strobed by IGO:
READ. The Model F880 tape transport reads data records of file marks in either a
forward or reverse direction, generating output data (eight lines plus parity) and data
strobes to the controller. A read reverse into load point clears the formatter in the same
way as does an IFEN reset. A read forward operation will be terminated if it occurs
more than 15 feet beyond EOT. This prevents transport operation, which could cause the
tape to run off the end of the supply hub. Recovery threshold is automatically lowered
during a read operation in order to provide additional reliability. The write threshold is
approximately 2596, while the read threshold drops to 10%. The beginning of a data block
is detected by the presence of two or more data channel envelopes which exceed the
threshold for 15 to 20 consecutive character intervals. For purposes of End-of-Block
detection, the presence of less than two channels for 15 to 20 consecutive character
intervals generates Gap Detect and drops IDBSY. During the read operation, error
detection, data transfer, and file mark search occur. These lOSSY lines may be strobed
by the trailing edge of IDBSY. They remain valid for at least 1 and no longer than 100
microseconds.

SPACE (Forward and Reverse). This operation is identical to a standard Read, except that Read Strobe and error flags are not generated.
FILE SEARCH. This signal initiates a space operation in either the forward or the
reverse direction. The read data lines may be deactivated during file search operation,
thereby ignoring any data that is written on the tape. The File Search command is
terminated when:
a.

A file mark is encountered.

Load point is encountered in a reverse direction.

The formatter is externally cleared.

The tape is past EOT by 15 feet or more.

WRITE (Forward only). The Microstreamer tape transport starts tape and generates the
proper delay before transferring the data character, ensuring the generation of
com patible inter-record gaps. When writing from load point, the dual-speed tape drive
always generates the required PE identification burst. When lOSSY goes true, it
indicates that the first IWSTR (write strobe) will occur no sooner than 40 character
intervals later. The write operation continues until ILWD (Last Word) is received by the
transport, which indicates the last character in the data block.
True write operations (not erase) generate an automatic read verification with the
signals activated as in read commands, except that signal thresholds are higher (25%).

COMMAND

REVERSE

WRITE

WRITE
FILEMARK

EDIT

ERASE

Read Forward

Read Reverse

Read Reverse Edit

Write

Write Edit

Write File Mark

Erase Variable Length

Erase Fixed Length

Security Erase

Space Forward

Space Reverse

File Search Forward

File Search Forward
(Ignore Data)

File Search Reverse

File Search Reverse
(Ignore Data)

No Operation Decode

3200 bpi*

1600 bpi (PE)*

Diagnostic Routine

Cycle Servos
Exit Test 22 Any Command

Read Logic Margin Test

+5 Vcc Circuit Margin Test

Reset Margin Tests

Extended Status

*Microstreamer 2 only

Table 3. Command Decoding

There are several variations to the basic write operation, as .explained in the following
subparagraphs.
EDIT. This signal is identical to basic write operation (or its variations), except
that erase and write head currents are sequenced on to over lap the record being
rewritten. This operation should be preceded by a read reverse or read reverse edit
command to position in front of the block being'edited. A block should be edited no
more than three times to ensure proper gap spacing.
VIRlTE FILE MARK. This signal generates the compatible file mark and produces a
(4.0-mch) IRG gap. The read file mark circuitry is activated. If a file mark status
is not returned, the file mark should be backspaced and rewritten. File mark
identification is reliable, since it is recovered by means of majority gating. All
required and optional tracks are being written with 80 transitions (40 characters) of
O's. ChanneJs 1, 3, and 4 are dc erased.

ERASE. This signal produces an erase field at the head with no data flux transitions.
There are three variations to this command, as follows:

ERASE FIXED LENGTH: erases a fixed length of tape (4 inches).
ERASE VARIABLE LENGTH:
continuous erasure until terminated by the
controller. Length is determined by the last character flag used in a normal write
operation.
SECURITY ERASE: erase forward to EOT and 5 feet beyond. No status lines are
activated; other transports may be selected while a SECURITY ERASE is
occurring. It is not necessary to wait for IFBSY to drop before selection of another
transport, but it is preferable to wait for IDBSY. The transport may also be
commanded to rewind after completion of SECURITY ERASE simply by issuing a
REWIND. The transport will indicate an immediate rewinding status, dropping the
IDBSY, IRDY, and IFBSY, but will complete SECURITY ERASE and a REWIND
automatically. Other transports may be selected and used during execution of
these com mands.
NO-OPERAnON DECODE. This command specifies no operation of the transport, and
may be used to stabilize the command lines during extended inter-record gap operation.
3200 BPL This is a command which,· when initiated while at the BOT marker, specifies
the 3200 bpi mode of operation. This option is available only on the Microstreamer 2.
1600 BPL This is a command which, when initiated while at the BOT marker, specifies
the PE mode of operation.
DIAGNOSTIC ROUTINE. This is a command which, when initiated, redefines the
command coding to allow the selection of internal diagnostic routines while the transport
~ L., the cn=line mode. Tr.e subsequent command, which seleCts tr.e specific diagnostic,
must be available within 1 second of the ON-LINE DIAGNOSTIC command.

Cycle Servos: (Identical to Service Aid 22)

Read Logic Margin Test: (identicai to Service Aid i i)

+5 Vcc Circuit Margin Test: (Identical to Service Aid 13)

Reset Margin Tests: (Identical to Service Aid 12)

Extended Status: The transport will output 128 bytes of information in the
form of 256 nybbles (half-bytes) with the low nybble of each byte first. The
user must pack the nybbles to restore the byte information.

READI\VRITE DATA LINES
IWSTR. This is a pulse indicating (trailing edge) that the character on the data lines has
been written on tape and the next character is needed. The next-character and last-word
flag must have a set-up time of at least 300 nanoseconds ahead of the trailing edge of
the IWSTR. This timing is illustrated in Figure 11. The frequency of the WSTR pulse is
proportional to tape speed multiplied by bit density. The width of IWSTR is 2.0 (:1:0.1)

IGOU
IOBSY

~----------------------~/,~'-----

IWSTR

ILWD

,.;////////!/

o/IJ

= 300 NANOSECONDS (MINIMUM)

= 25.00 MICROSECON OS @ 25 IPS
= 6.25 MICROSECONDS @ 100 IPS

0 NANOSECONDS (MAXIMUM)

Figure 11". Write Strobe Timing
microseconds. The following equation represents the relationship WSTR frequency to
tape speed and bit density:
fw = (v) X (bpi)
e.g.: @ 100 ips PE

loW

n nl'\n

J.O·J,·Jij'J

b'"
I
-d
YLes,seCon

4-21

awn.

This is a flag associated with the last write data character. The set-up time must

be at least 300 nanoseconds ahead of the trailing edge of IWSTR. There is no hold time

requirement. This flag is also used to terminate the WRITE command and Erase Variable
Length command.
IWP, 1'1'0-7. These are Write Data Lines. They must be set up with the same timing as
ILWD.
IRSTR. This is a pulse which indicates that a read character is present on the controller
interface. Note that although average long term transfer rate is the same as for write
data, due to skew and velocity change, the instantaneous rate can be almost twice that
of the write data. The fall of lOSSY should be used to indicate the end of the command,
since not all read and write commands will produce read strobes. Figure 12 illustrates
IRSTR timings.
IRP, 1R0-7. These are read data lines to the controller.. Timing is indicated in Figure
12. The read data lines overlap the IRSTR by at least 500 nanoseconds"

IRSTR

...

=ox

-I
I

IRP,IRO-IR7

Ic
I
I.-n
I

•

I1.I

I
I

~
I
I

I
I
I

I
I

I
I
I

~T3

I
I

T 1 (MINIMUM)

= 100 NANOSECONDS

T2 (MINIMUM)

= 3.5 MICROSECON DS @ 100 IPS
= I", MICROSECONDS @ 25 IPS

T2 (AVERAGE)

= 6 MICROSECONDS @ 100 IPS
= 25 MICROSECONDS @ 25 IPS

T3 (N OMIN AL)

= 1.5 MICROSECONDS 0.5 MS)

T4 (MINIMUM)

- 500 NANOSECONDS

Figure 12. Read Strobe Timing

PLUG
NO.

LIVE
PIN

GRD
PIN

. SIGNAL

TYPE

FUNCTION
When true, during write, indicates that
the character to be strobed into the
formatter is the last character of the
record.

Last Word (lLWD)

Level

Write Data 4 (lW4)

Level

Initiate Command
(lGO)

Pulse

·With MTSU ready and on line, the
command specified on the command lines
is initiated on the trailing edge of IGO •

Write Data 0 (lWO)

Level

Write Data 1 (lW I )

Level

Reverse (tREV)

Level

When true, with MTSU ready and online,
causes tape to move in the reverse
direction, and when folse, causes tape to
move in the forward di rection.

Rewind (lREW)

Pulse

With MTSU ready, online, and not at
BOT, this pulse causes tape to rewind in
reverse direction.

Write Data Parity
(lWP)

Level

•

1---

Table 1-2. Interface Input Connections

PLUG
NO.

LIVE
PIN

GRD
PIN

SIGNAL

TYPE

FUNCTION

Write Data 7 (WD7)

Level

Write Data 3 (tWD3)

Level

J:.

lJI

Write Data

6 (tWD6)

Level

Write Data 2 (tWD2)

Level

Write Data 5 (tWOS)

Level

Write (lWRT)

Level

When true, specifies the write mode of
operation, and when folse, specifies the
~ead mode of operation.

. 39

Erose (lERASE)

Level

When true, with MTSU on line, specifies
the erose mode of operation

Write Fi Ie Mark
(lWFM)

Level

When true, and IWRT is also true, causes
a file mark to be written on the tope.

Formatter Enable
(lFEN)

Pulse

With MTSU, on line, and IDBSY true, the
pulse wi II reset a command "runaway"
condition.

Table 1-2. Interface Input Connections (Continued)

PLUG
NO.

LIVE
PIN

GRD
PIN

Rew i nd/Un load
(IREW)

Pulse

When true, with MTSU on line, causes
the selected unit to go off line and
rewind tape to the BOT marker. The
MTSU will unload the tape when BOT
marker is detected.

49 ..

High Speed Select
(lHISP)

Level

When asser-ted I microsecond ahead of
the trailing of IGO, causes the transport
to operate at 100 ips.

Transport Address 0
(lTADO)

Level

The MTSU is selected by a combination
of the levels on the IT ADO, IT AD I, and
IF AD lines and the position of switches
5 I, 52, and 54. Refer to Volume I,
Section II.

Transport Address I
(lTADI)

Level

Format ter Address
(IF AD)

Levell

Edit (lEOIT)

Level

SIGNAL

TYPE

FUNCTION

When true, with IWRT true, causes the
MTSU to operate in the edit mode.

Table 1-2. Interface Input Connections (Continued)

PLUG
NO.
-----

LIVE
PIN'

GRD
PIN

SIGNAL

TYPE

FUNCTION

Level

Goes true on trailing edge of IGO, when
a command is received by the MTSU, and
remains true for duration of the
commande

Read Data 2 (lR2)

Read Data 3 (lR3)

Read Data Parity
(IRP)

Read Data 0 (lRO)

Read Data (IR I )

Load Point (lLDP)

Level

Read Dato 4 (lR4)

Read Dota 7 (lR7)

Reod Doto 6 (lR6)

Formatter Busy
(lFBY)

Tobie 1-3. Interfoce Output Connections

True when BOT marker is positioned in
front 0 f photosensor.

PLUG
NO.

LIVE
PIN

GRD
PIN

Hard Error (IHER)

Pulse
or
Level

When true, indicates that on
uncorrectable read error has been
detected by the MTS~.

File Mark (IF MK)

Pulse

When true indicates that the MTSU has
detected a fi Ie mark.

Indent ification
(IIDENT)

Level

Goes true, when the BOT marker passes
over the read head, to ident ify 1600 bpi
(PE) tapes •

SIGNAL

FUNCTION

TYPE

Read Data 5 (IRS)

End of Tape (IEOT)

Level

When true, indicates thot the EOT
nlarker has been detected. IEOT remains
true until the "EOT marker is sensed in
the reverse di rection.

Ready (IRDY)

Level

True when load sequence is complete and
MTSU is on line and not rewinding.
(MTSU is ready to receive a remote
command.)

Table 1-3. Interface Output Connections (Continued)

•

PLUG
NO.

LIVE
PIN

GRD
PIN

Rewirding (lRWD)

Level

True vhen MTSU is selected and a reel
of tape without a write-enable ring is
mounted on the MTSU.

Read Strobe (lRSTR)

Pulse

Goes true for each data character read
from the tape.

Write Strobe
(lWSTR)

Pulse

When true
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