Digital PDFs

DIGITAL-7-94-U

January 1966

8 pages

Original

0.2MB

Document:	DECTAPE COPY
Order Number:	DIGITAL-7-94-U
Revision:
Pages:	8
Original Filename:	http://bitsavers.org/pdf/dec/pdp7/DIGITAL-7-94-U_DECTAPE_COPY_Jan66.pdf

OCR Text

IDENTIFICATION

1.1

Dig ita 1-7-94- U

1.2

DECtape Copy Program

1.3

January 21, 1966

FDF

LIBRARY

Di gita \-7-94-U
Page 1

ABSTRACT

The program is designed to copy all or part of any DECtape onto any other DECtape. The
program reads a series of blocks, writes them on the second DECtape, and then rereads them checking for
an accurate checksum and comparing the information just read with the information origina Ily read. Any
DECtape or comparison error will cause an identifiable halt. To keep the programming simple and to
allow maximum space for copying purposes, block number references are entered using the console ACCUMULATOR switches. The program operates on either a 4K or 8K PDP-7. It is not designed for operation
on a PDP-4.

REQUIREMENTS

3. 1

Storage

The program occupies approximately the first 1400 locations of core memory but uses the
remainder of memory through location (1) 7377 for copying and comparison areas.
3 .2

Subprograms

The program makes use of the PDP-7 Bidirectional DECtape Subroutines (Digital-7-22A-I/O),
with which the symbolic tape must be assembled. The subroutines are included in the binary tape used for
running the program.
3.3

Equipment

Two DECtape drives attached to a PDP-7 DECtape control are required. The PDP-7 can
have a 4K or larger memory.

USAGE

4.1

4.1 .1
Mount the tape to be copied on a DECtape drive dialed to unit 1. The drive can be kept
in WRITE LOCK position.
4.1 .2
enabled.

Mount the tape to be copied on a DECtape drive dialed to unit 2. The drive must be write

4.1 .3

Read in the binary tape by starting at location (1) 7770.

4.1 .4
Set bits 8-17 of the ACCUMULATOR switches to the first block to be copied (numbers 1-1100
only); then start at location 22.
4.1.5
When the computer halts, set bits 8-17 of the ACCUMULATOR switches to the last block
number to be copied, and press CONTI NUE .
4.1 .6
When the computer stops at location 134 with the accumulator and link set to all l's,
copying has been completed. To copy another section, repeat the steps beginning at paragraph 4.1 .4
using the required set of block numbers. Do not press CONTI NUE.
4.2

Calling Sequence (Not Applicable)

Digital-7-94-U
Page 2
4.3

Switch Settings

The ACCUMULATOR switches must be set to the starting block number before starting at 22,
and to the final block number after the halt, which occurs immediately. Bits 6-17 are examined even
though block numbers 1-11 00 on Iy are accepted.
4.4
The program can be restarted any time by setting the ACCUMULATOR switches to the first
block to be copied and pressing START with the ADDRESS switches set to 22.

4.5

Errors in Usage
The followi ng errors can occur:

Ha It Location

Meaning

Procedure

Illega I CAL i nstructi on.
Probable machine malfunction.

Re load the program and start over.
If condition persists, the computer
requires maintenance.

HALT to allow putting final
block number in the ACCUMU LA TOR swi tches . Not
an error.

Set ACCUMULATOR switches to
final block number to be copied,
and press CONTINUE.

134

Final halt. Accumulator and
link should be all lis.

Repeat program for additional areas
to be copi ed, as necessary.

202

Interrupt occurred from other
than DECtape, or a DECtape
skip command did not function correctly. The ACCUMULA TOR displays the result
of an IORS command.

Start over. If error persists, maintenance shou Id be performed to
eliminate the spurious flag.

217

DECtape error during reading
of original tape. The contents
of the ACCUMULATOR Ii ghts
i ndi cate the type of error as
follows:

Press CONTINUE to try operation
again. If the error is persistent,
either the DECtape cannot be copied or the DECtape system itself is
malfunctioning. Try copying another tape or section of tape, if
possible.

LA W 100 - Forma terror (shou Id
never occur)
LAW 200 - Block number cannot be found
LA W 300 - Non-end-of-tape
error duri ng
searching

Digital-7;...94-U
Page 3

Ha It Locati on
217 (cont)

Meaning

Procedure

LAW 400 - Error flag during
reading
LAW 500 - Sum check error
during reading
LAW 600 - Error flag during
writing
LAW 700 - Block-mark number
error duri ng reading or writing

221

Dectape error during writing
of new tape. See HL T 217
for decodi ng of error.

Same as above

223

DE C tape error duri ng reread
of second tape. See HL T 217
for decodi ng of error.

Same as above

225

Comparison error.

Press CONTI NUE to reread and
rewrite the last section. If error
persists, maintenance is required.

RESTRICTIONS

The tapes copied must be in the standard DEC format of 11 OOS blocks of 400S words each.
Note that block 0 cannot be copied.

DESCRIPTION

6. 1

Discussion

The program first determines whether or not a 4K machine is used and allocates core locations accordingly. If a 4K machine is being used, 3000S locations (6 blocks) are allocated for reading
and an additional 3000S locations are allocated for checking. If an SK machine is used, 7000S locations
(16S blocks) are allocated for each area.
The copying procedure is as follows:
1. Read (1)6 blocks from the original tape, in either direction.
2. Write the (1)6 blocks on the second tape, in either direction.
3. Reread the (1)6 blocks from the second tape, in either direction, into another core area and compare the two areas.

4. Repeat steps 1-3 unti I a" requested blocks have been transferred, then ha It.

Digital-7-94-U
Page 4
6.2

Applications

The program can be used to copy any standard type of PDP-4, PDP-6, or PDP-7 DECtape
without reference to the contents or data format on the tape providing only that the standard block format
is used. It is, therefore, a fairly fast procedure for copying system tapes or other work tapes. This allows
duplication of tapes for backup or for distribution to more than one user.

METHODS
(See Discussion, Section 6)

FORMAT

Standard PDP-4, PDP-6, and PDP-7 DECtape block format of 11008 addressable blocks of
4008 (l8-bit) words each.

Execution Time

Measurements indicate that a complete reel of tape can be copied and checked in almost
exactly 3 minutes using an 8K computer, or about 4 minutes and 20 seconds on a 4K computer.
10.

PROGRAM

Program Listing is attached. See Digital-7-22A-I/O for a complete listing of the PDP-7
Bidirectional Subroutines which are not included with the listing of the Copy program itself.
10. 1

Core Map (None)

10.2

Dimension List (None)

10.3

Parameter List (None)

10.4

Program Listing
IT.'~

ILMII4

Copy P~OBRAM

'.2'-66

211

ao,

Got.

I-4LT

eA'
LAC CJMP INTERR)
DAn t
LAC (NOPt
DAe !wt
OZM 17"
nZM t7,7,
OAt'! t777'
gAD 1777
JMP m03
LAn ( t 6)
DAe Kt
LAC (7000)
rlAe 1<2
L.A/'! 1<,
eMA

lei'EAR 'LAGS

18,T UP !NTER.U.T
II,T swt
IS~IP

IF AK MACHINE
HAeMIN!
INI'IMB£A 0' 81.001(1 flER PA8s
I.~

IN"MB[1It 0, WORDS .ER PASS

Digital-7-94-U
Page 5

OAt'!
LAe ~1.1
ADn 1(2
OAe R3-1

TAn (.0)
-bAC

rlAe R2

ADD 1(2

DAe R3
LAS
AND (7'77'
ADD
DAe eN
~L"

G03.

IRIAn DATA
R~,

LAS
AND <7777,
DAe 1(2
JMP Sw,+1
LAC! (6)

~h.N

~A'

FtA,

JM! WAtT
JMS MMWRS
LAC eN
JMP ERRi
20000
FtA,

RiA,

~A'

JMS WAIT
JM~ MMRDI
LAC BN
JMP rRR"

20000
R~,

ICOM~ARr T~E

ISlIiTR"ACT 1
I!~D 0, 1ST RrlO AREA
1317100 "R ,000
IEMO or 2ND RrAD AREA

ISTARTtNG SLOeK

ISTARTtNG BLOeK-SIOcK DJSTANC[
IPI1T IN FfNAL. BLOeK
ILAST 9L.Oel<

JMS MMRDS
'0000

Ri,

IS,ART OF ·2ND REAn AREA

DAe 1(,

JMP ERR1

R1A.

1317100 nR ,000

LAC (3000l
JMP G02
LAC

R1,

1.~LOCI( DISTANOE
IS,ART of 'ST REAn AREA

RA2

RA2
JMS WAIT

IREAD
IBI'OCK NUMBER
I£~ROR
IU~.!I T

RETURN

IF,RST ADDRESs
IL~ST ADDRESS, MOnlFIED
IWRtTE
IBI'OCK NUMBER
I[~ROR RETURN
IUMIT
I',RST ADORESI.
ILAST ADDRESS. MonlFIED

IREAD AGAIN
18j'OCK NUMBER
I!~ROR

RETURN

IUMIT
I"RST ADDRES~, MnDIFJ!O
ILAST ADD~£SI~ MOnIFI£D

Two AREAS
LAw RAt-'
DAe AX'
LAM
TAD Rl."'
CAe A)(2
LAC R3
OMA

ADD R3.1
OAe Of

IC",UNTr,R

Di9ital-7~94-U

Page 6

LAC r AX,
filA" r AXi

R'"

SKP

JMP rRR4

I£~ROR

rS! 0 .. '

JMP R4

swt,

NOP
LAC AN

IO~

ADD Kit'

IC"NSTANi SLO~I< AMOUNT

DAC eN
ADO 1<'
OM'
ADD 1<.2
ADD ( t ,

aMAvCLL
JMP R0
ADD 1<,
RTL
RTL
RTl
RTl
TAD (-0)
!lAC 1<,
LAC Rt·'
ADD 1(,
DAC R'
OAC R2
LAC ~3.'

HI.T

ICt'lNSTANT BLOel< AMOUNT
I',NAI. BL.OCK
IlAST ~ECTION TO ,AANg'ER
IT~ANS'ER NEXT
IC"NSTANT BLOel< AMOUNT
IMULTlpLY BY ,00

ISqBTRACT
IT,MPORARv STnRAG,

ADn 1<,

!lAC R3
LAC (STL.vCLCVHLT)
OAC swt
JMP R0
OAC AC~ .. AV£
MMrF'

!NTrJ:H~,

~KP

JMP I MMERR
MMnF'
~KP

JMP I MMOA'.
MM9F'
SKP
JMP I MM8LF'
IORS
IoILT

I 1,
"IS~'S.JMP

•

~A'

LAC 01
~AL

LAC ACSAV[
rON
JMP I
MMA"!,

II ~ITEFUtUPT [RROR

Digital-7-94-U
Page 7
0

LAC I MMWA1

IS! MHDON!
JMP ,.2
JMP I WAIT

ERR.,

~l.T

£RR2'

IE~R

DURING INITIAL READ

WLT
JMP R1A

I[~R

DURING WRITING

t-ILT

IE~R

DURING 2ND R,-AD

JMP R0

[RR3~

JMP R2A

ERR .. ~

~LT

JHP R0

AX1.'0
A)(2.A)(t ••
RA,., .. ",
RA2.Ii1.'.3B00
STAR'
11.

DIAGRAM (None)

12.

REFERENCES (None)

ICr\MPARISON ERROR