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DEC-08-LHAA-D

December 1967

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Document:	dec-08-lhaa-d
Order Number:	DEC-08-LHAA-D
Revision:
Pages:	8
Original Filename:	https://svn.so-much-stuff.com/svn/trunk/pdp8/src/dec/dec-08-lha/dec-08-lhaa-d.pdf

OCR Text

I DENTI FICAT I ON
Product Code:

DEC-08-LHAA-D

Product Name:

Date Created:

April 1 , 1967

Maintainer:

Software Service Group

HE LP" LOA DER

m
LIBRARY

DEC-08-LH AA-D
\

ABSTRACT
The "HELP" Loader loads the standard version of the RIM and BIN Loaders into the PDP-8, in

less than 90 seconds, replacing manual procedures which required several minutes.

PRELIMINARY REQUIREMENTS
Teletype Model ASR33 a standard PDP-8 or 8/S

LOADING PROCEDURE
a.

Load the following routine starting at LOC. 27:
27/
-.*

6p31
5027
,6036
7450
5027
jOl2
Tolo
' 3p07
t
'2036
,5027

GO,

KSF
JMP.-1
KRB
SNA
JMP 27
RTR
RAR
DCA 7

ISZ 36
JMP 27

Place "HELP" tape into ASR33 Reader

Set Reader switch to START

d. Load SWITCH REGISTER with 27
e.

Depress LOAD ADDRESS switch

f . Depress START switch

STORAGE
Loader uses 26

locations (5-36).

These should be octal.

DETAILS OF STORAGE A N D OPERATION
a.

The source tupe, called the "Help Generator," i s a two part program and functions in a

straight forward way.

Part 1 punches out part 2 which becomes part of the load routine when read in.

Behind this are the RIM and Binary Loaders.
b. Each of the first 21 lines on the "HELP" Bootstrap Tape becomes an instruction which w i l l
comprise a new loader which in turn loads the rest of the tape.
The 17th line loaded into the AC becomes a JMP 10 instruction which i s loaded i n location
27. Now, notice how control i s switched from the program entered by the switches to the newly loaded
7

program.

DEC-08-LHAA-D

37/
40/

ISZ
JMP

36
27

When the instruction JMP 27 i n location 40 i s executed, the PC goes to 10, which contains
the first instruction of the newly loaded loader.

This new loader now loads the rest of the tape i n a

format where a 12-bit word i s contained on L o lines of tape.
The first 12-bit word formed i n the new format i s 3407, this i s loaded into location 23.
Location 23 previously contained the instruction DCA 23.

This means that our new loader has been

modified so that the rest of the data to be loaded w i l l be deposited indirectly through location 7.
A t the moment, location 7 contains the number 6.

The next two lines read contain the num-

ber- 7402 which w i l l then be deposited into location 6. This HLT instruction w i l l be the one which halts
the machine when loading i s complete.

The new loader modifies location 7 to contain 7, which w i l l be the address of the next 12-bit
word.

The number 7577 w i l l then be loaded into location 7. This effectively switches the: loading

point to the starting address minus 1 of the binary loader.
When the modified program has loaded the first 23 lines, pertinent core locations look like

5
KSF
JMP
KRB
RTL
RTL
RTL
DCA
KSF
JMP
KRB
TAD
DCA

ISZ
JMP
JMP
JMP
JMP
KR B
SNA
JMP

5
17

5
23
7
10
6
10
27

/Used to load DCA 17

/Formerly a KSF

The rest of the bootstrap tape contains the RIM and BIN Loaders which are about to be loaded
at this point.
When these two loaders are stored i n the proper cgre positions, the content of location 7
reaches zero.

When i t reaches zero, the instruction 5301, i .e./ JMP 7701, i s loqded into core loca-

tion 7777. This i s the last instruction to be loaded and therefore the loading process halts.

DEC-08-LHAA-D

When location 7 reaches zero the program skips the instruction following the ISZ 7 in location 24.

From location 26, the program branches to location 6 which contains the HLT.

Core Space Required
The actual bootstrap loader takes up locations 5 through 36 (26,0) to load the RIM and BIN
Loaders into the last page in memory.
Execution time i s approximately 90 seconds.
c.

To get the Bootstrap Loader tape from the HELP generator BIN object tape.

(1) Using the BIN Loader, load the HELP GENERATOR program into core.
(2) Turn on the punch on the ASR33.

(3) Start the generator program a t 7400.
NOTE: The RIM and BIN loaders punched on the Bootstrap Loader Tape
are the ones currently in the machine.

LISTING

/HELP PROGRAM
/NOTE: RIM AND BIN LOADER MUST BE IN CORE
/BEFORE USING THE SOURCE PROGRAM
/TO GENERATE THE BOOTSTRAP LOADER.
*7400
7400
740 1
7402
7403
7404
7405
7406
7407
7410
741 1
7412
7413
7414
7415
7416
7417
7420
742 1
7422
7423
7424
7425
7426

7300
6046
1253
3254
1250
3256
1250
325 1
4242
225 1
5210
1656
4242
2256
2254
5213
1656
7012
7012
7012
0252
4242
1656

LOOP,

LOA DER ,

CLA CLL
TLS
TAD KOUNT
DCA KOWNT
TAD BGIN
DCA START
TAD BGIN
DCA COUNT
JMS PUNCH
ISZ COUNT
JMP .-2
TAD I START
JMS PUNCH
ISZ START
ISZ KOWNT
JMP LOOP
TAD ISTART
RTR
RTR
RTR
A N D MASK
JMS PUNCH
TAD ISTART

/CONTAINS CONTENT OF FIRST
/ADDRESS TO BE PUNCHED
/CREATE SOME BLANK TAPE
/DONE PUNCHING BLANK TAPE?
/N 0
/MODIFY ADDRESS IN START
/DONE WITH FIRST SECTION?
/NO, GO BACK
/NOW START PUNCHING BINARY
/CONTENT ON 2 LINES OF OUTPUT

/SAVE LEFT HALF OF WORD
/PUNCH I T

D EC-08-LHAA-D

7427
7430
743 1
7432
7433
7434
7435
7436
7437
7440
744 1
7442
7443
7444
7445
7446
7447
7450
745 1
7452
7453
7454
7455
7456

0252
4242
2256
5220
1250
325 1
1255
4242
225 1
5235
7402
0000
604 1
5243
6046
7200
5642
755 1
0000
0077
775 1
0000
0200
0000

755 1
7552
7553
7554
7555
7556
7557
7560
756 1
7562
7563
7564
7565
7566
7567
7570
757 1
7572
7573
7574
7575
7576
7577

0050
0317
0102
0367
0067
0067
0067
005 1
0317
0172
0367
0054
023 1
0075
0106
0066
0102
0034
0007
0074
0002
0075
0077

PUNCH ,

BGIN,
COUNT,
MASK ,
KOUNT,
KOWNT,
COD200,
START,
*7551

A N D MASK
JMS PUNCH
ISZ START
JMP LOADER
TAD BGIN
DCA COUNT
TAD COD200
JMS PUNCH
ISZ COUNT
JMP .-3
HLT
0
TSF
JMP .-1
TLS
C LA
JMP I PUNCH
755 1
0
77
27
0
200
0

/PUNCH THE RIGHT HALF
/MODIFY ADDRESS

/PUNCH CHANNEL 8
/DONE?
/N 0

/7551 IS USED AS A S.A. AND AS A COU N T E R

/NO. OF I N S T . FROM 7751TO7577

50
317
102
367
67
67
67
51
317
172
367
54
23 1
75
106
66
102
34
07
74
02
75
77

/5 (GETS PUT IN LOC. 7 AS 1ST INSTRUCTION
OF NEW PROGRAM)
/KSF
/JMP 10
/KRB
/RTL
/RTL
/RTL
/DCA 5
/KSF
/JMP 17
/KRB
/TAD 5
/DCA. 23
/ISZ 7
/JMP 10
/JMP 6
/JMP 10 (TRANSFERS CONTROL TO NEW PRO)
13’407

IS A DCA I 7

/7402 IS A N HLT
/7577 IS THE S.A. OF BIN LOADER-1

BGIN 7450
COD200 7455

COUNT 7451

DEC-08-LHAA-D

KOUNT 7453
KOWNT 7454
LOADER 7420
LOOP 7413
MASK 7452
PUNCH 7442
START 7456