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DEC-7U-YXTA-D

October 1969

12 pages

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Document:	DECTOG
Order Number:	DEC-7U-YXTA-D
Revision:
Pages:	12
Original Filename:	http://bitsavers.org/pdf/dec/pdp7/DEC-7U-YXTA-D_DECTOG_Oct69.pdf

OCR Text

PDp·-7 PROGRAM LIBRARY

DEC-' 7U- YX 'J.1A:'" D

1.1

PDP-4/7 DECTOG JR.

1.2

October 1, 1969

2.0

ABSTRACT
DEctog Jr. allows the user to format and certify DECtapes
using ·the toggle switches of a PDP-7 or PDP-4 computer.
The routines will allow the formatting of tape to the
Standard Format for DIGITAL's 18 and 36-bi·t computer
lines [i.e., 11028 blocks per tape with 1536 data lines
(3 bits per line) per block].
The ·tapes formatted by this program differ in three ways
from the tapes formatted by DECtog (DIGITAL 7-20-IO-FB).
a.

Check-sum is calculated by XORing six bit bytes.

199 additional space codes are written between
the end-zones and ending blocks on tape.

All blocks on tape are exercised (from block 0
through 1101 8 ).

The addition of more space codes enable the tapes to be
used with the PDP-7/9 ADVANCED Software.
The user simply sets the ACCUMULATOR switches, as required,
and starts the computer at the correct starting address
for the particular program.

'rhe appropriate messages will

be typed when the function is completed or when any error
occurs.

A brief description of each program is given

in the following paragraphs.
current

programs

However, a list of the

and their starting addresses follows:

Star"ting
Address

Mnemonic

Function

2.1.1

100

RWMK'l'R

Mark track writer for PDI
compatible DECtapes.
Use prior to WRNVT below.

2.1.2

101

WRNVT

Second pass virgin tape
program· for revised mark
track writer.
(To be used for, and
after, RWMKTR above, only

2.1.3

102

EXER

Exercises requested
tapes by writing a
pattern of all ones and
all zeros and sum-checking in both directions.

NOTE:

3.0

The preceding three programs must be run in
succession to produce a properly formatted
DECtape.
The following two programs are used
only to check the block numbers on a tape and
are not required for formatting.

starting
Address

Mnemonic

2.1.4

103

RBMN

Reads block numbers from
requested tape into successive locations, beginnin c
at 3600.

2.1.5

104

RBMNR

Reads reverse block numbers
from requested tape in
reverse direction into
successive locations beginning at 3600.

Function

EQUIPMENT REQUIREMENTS
Paper Tape Reader, Teleprinter, DECtapes

4.0
DETOG JR. is written in the PDP-7 Basic Assembler
language. The object binary tape is in Funny Format to load
DETOG JR.

5.0

READ-IN the RIM loadE~r at 17763

Load DETOG Jr. in the reader and set the address switches
to 17770 and press START.

(for the PDP-4, the RIM
loader must be toggled in by way of the cons91e switches).

USAGE
5.1

Errors

5.1.1

All error messages have the following format:
ERR XXX ZZZ (Y)*
where ERR is the code for the error, XXX is the
block involved, and ZZZ is the nine bits of the
report of the DEctape status using the MMRS instruction.
The bits can be interpreted as follows:
Bit O=Data flag up
l=Block flag up
___ .?=~~!qE . :~!.~q .. ~E
3=End of tape
4=Timing error
?::=R~yerse

6=Go
7=Mark track error
8=Unable

If an error occurs in the exerciser, y will indicate
the offending unit number (in octal).

5.1.1

(can tinued)

Error Codes are as follow$:
FMT = Format Error.

Check ACS

NTF = Block number not found.
ERS

= Error flag for other than end of tape, during search.

ERR = Error flag during reading.
SUM = Sum check error.
ERW = Error flag during writing.
BMW = Block mark read does not correspond to block mark
predicted during writing.
BMC = Block mark read does not correspond to block mark
predicted during sum checking.
INT = program interrupt occurred from other than error or
data flags of DECtape unit.
FLC = 'Jlhe block

~nd

flag occurred before or after 40Ch

data flags had been found.
writing virgin tape.

Can occur only during

count of the number of flags read; i.e., 400400
(where 400400=4008) or 377377 (where 377377=377 8 ) etc.
NFL = No flags.

program has stopped receiving program

interrupts from DECtape unit.

5.1.1

( continued)

BUF = contents of DECtape buffer were wrong after issuing
MMWR command and checking by MMRD.

occurs during

writing virgin tape only.
NWR = Actual check sums do not agree with predicted check
sums using exerciser, indicating that probably nothing
was written.

In the exerciser, unit 10 (Octal) will

always appear with this message.

Can also occur if

for any reason the first block in a pass was not
written (for example, NTF etc.).
NZB = No zero block.

WRNVT could not successfully write

the first zero block.
4.5.2

Rerun WRNVT.

When errors occur, the following registers may be
of importance.

Since binary tapes are supplied

with the DDT symbol table it is suggested that DDT
be used to read in DECtog and examine the indicated
registers.
MMRVC

The reverse check sum as read from
the block.

MMRDC

The forward check sum as read from
the block.

5.1.1

( continued)
The actual check sum calculated

MMCC

during reading.
The forward check sum as written on

MMWC

the tape during writing.

This should

agree with MMRDC if the same direction
is used ..
Usually contains the block number of

MMWAl

the block being transferred.
NOTE:

The forward check sum is the one read or
written after the data, and the reverse
check sum is the one read or written before
the data.

Therefore" both vary according

to the direction being used.

6.0

PESCRIPTION
The programs- will format tapes that may be used on the
PDP-l/4/7/9/10/l5.

The tape format is specified in the

PDP-9 Users Handbook (i.e., 11028 blocks per tape with
4008 words per block).

TO FORMAT A TAPE

6.1

RWMKTR
Two new programs have been designed to write the
mark track, virgin tape pattern, and to check the
tape.

These are described fully, below:

RWMKTR writes only the timing and mark tracks on the
tape.
a.

Usage is:

Place the reel as close as possible to the
physical start of the tape.

Set the switch which controls writing the
timing track to ON.

Set ACS, as follows:
012

345

'--.y--'

67S

9 10 11

12 13 14

15 16 17

Unit
d.

start at lOOS.

When program is finished, turn MARK TRACK switch
off,

remounttape if necessary, and continue with

the virgin tape program (WRNVT) explained below.

Used to write the virgin tape pattern and the block
mark numbers on a tape with a newly created timing
and mark track.

T~lis

program should never be used

except after RWMKTR above.·

It is not a normal virgin

tape program, but one which writes through block ends.
After the block mark numbers and virgin tape have been
writtep in the forward direction, the tape is automatically sum checked in reverse, showing all errors.

addition, the first block on the tape is rewritten to
guarantee a 0 as the first block mark number.

usage

is:
a.

set ACS as follows:
012

345

6.3

678

9 10 11

12 13 14

15 16 17

start at 101 8 _

EXER
Exercises a succession of tapes by writing

all

ones in the forward direction on all desired
tapes, sum checking in the reverse directon on all
tapes, sum checking in the forward direction on all
tapes, writing

all zeros in the reverse

direction on all tapes, sum checking in the forward

6.3

(continued)
direction on all tapes, and finally sum checking in the
reverse direction on all tapes.

,The entire cycle will

be repeated continuously until ACS bit 0 is made a 1.
A message is written at the end of each cycle giving

the octal number of the cycle.

The pattern written

during each pass is incremented by the pass number.
If an error occurs, the program will type a message
and continue, beginning with the next block.

All

error messages will indicate the unit number at the
end of the me'ssage.

The NWR message will stop the

program only if it occurs eiyht times.
a.

Usage is:

set AC switches 1-8 to a I to indicate which
units (numbered 1-8 respectively) are to be
tested.

For example, to exercise units 1-4 set

only swi tches 1·-4 to a I ~ to exercise uni t

3 only,

set switch 3 to a I and all others to a O.

Any

combination of bits may be used.
are examined.

Only bits 1-8

These switches can be reset at

any time ,during the running of the program to add
,.

or delete units.

If ACS O=l, the program will stop

at the end of a pass.

For purposes of thi~3

paragraph those persons using the most recent tape
drives numbered 0-7 should use bit 8 to indicate
unit

6.3

(continued)
b.

6.4

start at 1028 •

RBMN
Rewinds the indicated tape unit, then searches forward,
reading all block mark numbers and placing them
(wi thout masking) in successive locations beginning
at 3600.

When the :reverse end of the tape is reached,

the remainder of the area up through 7577 is filled
with

one's

(777777), thus making clear the

last block mark number found.
by using the EXAMINE key.

The area can be checked

For the standard tape,

block number 0 will be in location 3600 and number
11.01 will be in location 47.01.
a.

Usage is:

Set ACS as follows:

o 1\7~~

678
(

9 10 11

12 13 14

15 16 17

Unit
b.
6.5

start at 103.

RBMNR
This program winds the tape forward until the end
zone is reached, then searches in reverse, placing the
reverse block numbers read in successive locations in
memory b~ginning at 3600.

When the end of tape is

reached, the remaining locations through 7577 are

6. 5

(continued)
filled with

one's (777777).

For the standard

tape, block number 1101 will be in location 3600, and
block number 0 should appear in 47J1fl

The locations

can be looked at viath,e EXAMINE key.

Usage is:

set ACS as follows:

o 1 2 345
\. . __._y--_J
Unit
b.

start at 104.

678

9 10 11

12 13 14

15 16 17