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MAINDEC-11-D9EA

May 1972

11 pages

Original

0.4MB

Document:	Maintenance Loader
Order Number:	MAINDEC-11-D9EA
Revision:	0
Pages:	11
Original Filename:	http://bitsavers.org/pdf/dec/pdp11/xxdp/diag_listings/1140_45/002_D9EA_MAINT_LOADER.pdf

OCR Text

.. .... -.- ...
~.-

PRODUCT CODE:

MAINDEC-11-09EA

PRODUCT NAME:

MAINTENANCE ~OAOER

CATE CREATEO:

10 OECEMSER 1970

MAINTAIN£R:

OIAGNOSTIC GROUP

AUTHORSI

RICK rAOOEN, AND V VEROSTIC

MAINCEC-11-D9EA
PAGE 2
1.

AB?IRACT
THE PURPOSE Or THIS ~OAOER IS TO P~OVIDE AN A~TERNATt
METHOD or LOADING OIAGNOSTICS WHICH MAY rUNCTION WHEN TH£
ABSO~UTE LOAOER 'AI~S TO WORK OUE TO A HAROWARE rAl~UR~.
A
OESCRIPTION Of THE BOOTSTRAP ~OAOER LOAOING THE MAINTENANCE
~OADER IS ALSO PROVIOED TO AID IN ISOLATION or TRoue~E SWOULO
IT BE IMPOSSIBLE TO LOAD EVEN THE MAINTENANCE ~O'OER. THIS
~OAD£R IS NOT INTtNOED TO REP~AC£ THE ABSO~UTE LOAOtA AND
~HOY~D ONLY BE USED FOR LOAOING Or DIAGNOSTIC PROGRAMS Ir
THE ABSOLUTE LOAOtR WILL NOT rUNCTION,

REQVIREMENTS

2.1

EQUIPMENT
PDP·11/2~

2.~

STANDARD OOMPUTER

~TORAGE

THE PROGRAM UStS MEMORY LOCATIONS 11476 THRU 17776.
3.

LOADING PROCEDURE

3.1

METHOD
PROCEDURE rOR NORMAL BOOTSTRAP TAPES SHOULO BE FOLLOWEO.

STARTING PROCEOURE

4.1

CONTROL SWITCH SETTINGS
NONE

4.2

STARTING ADDRESS OR AOOR£SSES
175~0

4.3

PRO~RAM

ANDIOR OPERATOR ACTION

LOAO PROGRAM INTO MEMORY, (BOTTOM 4K)
SET SWITCH R£GtSTER TO STARTING AODRESS (175ee)
LOAD ADDRESS,
PRE~S ST.RT.

M~lNCEC·11·09EA

PAGE J
5.

OPE~~TING

PROCEDURE

5.1

OPEHATIONA~

SWITCH S~TTINGS

NO ~WITCHES USED

5.2

~UBROUT~NE

ABST~.CTS

THE ON~Y SUBROUTINE USED IN THE ~OAOER IS 'OR ~EAOER
OPERATION TO rETcH DATA. IT IS tNTEREO WITH A BRANCH
INSTRUCTION TO ITS STARTING ~OCATION, BE'ORE BRANCHING
THE PC IS SAVED iN R" (THIS Pc IS POINTING TO THE BRANCH
INSTRUCTION), EXIT IS DONE BY AUTO INCREMENTING or THE
SAVEe PC 'R,) ANO MOVING IT BACK TO THE PC (R?), THIS
ELIMINATES THE USE or OPERATIONS USING THE STACK (JSR&RTS).
5.3

PROGRAM ANDIOR OP~RATOR ACTION
OPE~ATING

1.
2.
3.
4.
5.

6.
1.

6.
6.1

INSTRUCTIONS,

USING THE BOOT ~OAOER, ~OAO THE MAINT ~OAOER TAP,.
THE DEVICE AODRESS USED wJ~~ BE CONTAINED IN 17116. Ir
THIS DEVICE ADDRESS IS lERQ THE MAINT ~OAO£R WI~~ NOT RUN.
P~ACE TH~ MAiNT ~OAO~R STARTING ADDRESS (1'5~~) IN THE
SWITCH REGISTER ANO PRESS ~O"O ADDRESS,
PRESS START,
CHECKSUM IS CONTAINEO IN T~E ~OWER BVTE or Re. (IN THE DATA
~IGHTS ArTER HA~T.)
THE ~QWER BYTE or THE OISP~AY S~OULO EQUAL
iERO UPON SUCCESS'U~ ~OADING Or THE TAPE.
IF THE LOADER H4LTS WHEN DONE IT IS ONLY NECESSARY TO PRESS
CONTINUE TO READ IN ADOIT10NA~ TAPES,
IF T~E ~OAOER H'~TS AT THE F"I~ ADDRESS. A CHECKSUM
ERROR HAS OCCURRED. MOVE THE PAPER TAPE BACK TO T~E
BEGINNING O~ THE CURRENT 8~OCK AND HIT CONTINU, TO TAY
AGAIN.

ERRORS

If AT TKE ENO O~ A SLOCK THE C~ECKSUM IS Nor ltRQ. ~ H~LT
AT LOOATION 17612 AND THE ~OWER ByTE or THE DATA ~IGHTS
CR0) CONTAINS THE rAU~TV CHECKSUM.

OCC~RS

6.2

ERROR RECOVERY
RECOVERY rAOM CHECKSUM ERRgRS MAY BE ACCOMP~ISHEO BY MOVING
THE TAPE BACK TO THE BEGINNING 0' THE a~OCK A~O PRESSING
CONTINUE TO ATTEMPT TO READ THE e~OCK CORRECT~V,

MAINCEC-11-09EA
PAGE 4
7.

RE~IRICTIONS

7.1

LOAOER WI~L OP~RATE IN T~~ ~ST 4K ON~Y (1152121), lr Ii
IS QESIROUS TO USE THIS IN AN EXPANOED SYSTEM AND P~ACE
ABOVE 175210. T~E rO~Low.%NG LOCATIONS MUST BE C~ANGED ONCE
THE MAINTENANCE LOAOE~ IS ~OAO£O INTO THE APPROPRIAi~ BANK.
THI~

X7521Z:;X747"
)(7510=X7414
X7542;;)(7415
)(7566=X7475
)(7624;;)(7176
)(7674=)(7414

7.2

)(

1 rOR 4K
3 rOR SK
5 rOR 12K

1;1

rOR 16K

11 rOF! 221K

13 rOR 24K
15 rOR 28K

THE MAINTENANCE ~OAOER HAS NO CAPABILITIES rOR RELOCATING
WHI~t LOADING.

pROg~AMS

MI?9ELLANEOUS

8.1

aOOlSTRAP LOADER SOURCE PROGRAM
THE BOOTSTRAP ~OAOER SOURCE PROGRAM IS SHOWN BELOW, THE STA~T~
ZNG ADD~ESS IN THE EXAMP~E DENOTES THAT THE LOADER 1$ TO BE
~OADED INTO MEMORV BANK ~EAO (A 4~ SYSTEM',

~17744

0177~0

kH'J0001
0002102

R11I"1

0114021

1..0AO'174"0

017744
"167"'1
~~02'26
2!127~2

OEVICE,R1

,USEO FOR THE DEYICe: ADDRESS
Justo FOA THE LOAD ADDRESS DISPLACEMENT
,DATA MAY ee: LOADED NO LOWER THAN THIS
,STARTING. AObRESS OF T~E BOOTSTRAP LOADER
IPICK UP O£Vlcr ADDRESS, PLACE IN Ri

A2="2

.=11744

STARTI

MOV

LOOF':

MOV

*.·LOAD+2,~2

JPX,CK UP AODRESS DISPLACEMENT

ENABLEr
WAIT:

.Rl

,ENABLE T~E PAPER TAPE READER

'R1
WAIT

116162

INC
T5T8
BPL.
MOVB

2(R1),LOAD(R2)

,WAIT UNTIL FRAM~ IS AVAILABI.e:
,STORE FRAME REAO FROM TAPE IN MEMORY

"0'267

INC

~OOP.2

,INCREMENT LOAD A.DDRESS OISPLACEMENT

~OOP

,GO eACK AND READ MORE DATA
JAODRESS or INPut DEVICE

(lJ00J52

017754
017756
2117760
017762

017710
017774
2117776

~215211

105711
100~H6
~002'02
e174~21

1717'6

2100765
02'0"0"

BRNeH.
OEV%CEI

8.~

MAINTENANCE LOAOER TA~E rORMA!
SPECIA~

~OAOING

BOOT LEAOER COOE COMES FIRST,
OFrS[T AS IS.

MAINCEC-11-0'EA
PAGE 5
THIS VALut LEAVES T~E

;J51
~51

;'51

,THIS IS THE AOO~ESS DISPLACEMENT WHICH WIL~ CAUSE T~E
.NEXT rRAME TO BE LOADED IN LOCATION 17476

MAINT
.THIS COCE 60405 AOORESSE.S 17476 THRU 177~0 WITH T~[
LOAOt R ,MAINTENANCE LOAOER CODE
030

.22 ,RAMES or ~ERO rIL~ IN THE REMAINING SPACE UP
,TO THE CODE WHICH RESTORES THE BOOT LOADER

000

THE rO~~OWING CODE IS LOADED STARTING AT 1'724. WHEN EXECUTED
IT WILL RESTORE LOCATIONS IN THE BOOT WHICH WERE MODIFIEO ANO
T~EN JUMP TO T~E HALT AT LOCATION 17.76,
367
~25

:'52
~00

020
000
367
025
365
001
034
i000

2,67
1?J00

Ult2767
'IUJ~3'2

U!12I12I02I?J

JfU2767
,1210"765
liQ0j0~"

,01210167

132

377

'l.775~2

THE ;OL~owtNC CODE IS LOADED OVER THE rIAST 4 LOCATIONS
IN THE BOOT LOADER, THE FIRST 3 ARE LEFT UNCHANGED, AND THE
4TH-MODI'IES THE BRANCH OFFSET TO CAUSE EXECUTION TO JUMP
TO ~OCATION 17724, AS NOTtO ABOVE, 17724 IS TME ST4RT 0' T~£
SECTIONWHtCH RESTORES T~E BOOT LOADER,
;'~1

035
026
000
~02

"'25

:573

1016'01
,01Z1R1ril26
'''12'0~

,"11.121373

MAIND~C·l1·09EA

PAGE 6
8.3

STEP BY STEP OESC~IPTION Or BOOTSTRAP LOADER O~ERATIQN (.K OPERATION)

THE BOOTSTRAP LOADER STARTS BY LOADING THE DEVICE STATUS
REGISTER AOOR~SS rROM 17776 INTO R1 ANO 352 INTO R2. THE
NEXT INSTRUCTION INITIATES A RtAO OPERATION IN THE DEVICE AND
THE NEXT TWO INSTRUOTIONS fORM A LOOP TO WAIT rOR THE READ
OPERATION TO BE COMPLETED. WHEN DATA IS ENCOUNTERED IT IS
TRA~SFERREO TO A ~OCATrON WHICH IS THE SUM Of THE INDEX
WORD (174Z~) AND THE CONTEN·S OF R2.
BECAUSE R2 IS INITIALLY 352.(8), THE FIRST WORD IS MOVED TO
~oCATION 11752, AND IT BECOMES THE IMMEDIATE OATA TO BE
PLACED IN R2 DURiNG THE NEXT EXECUTION or THE LOOP. THIS
IMMEOIATE DATA IS THEN INCREMENTED BY ONE AND THE PROGRAM
BRANCHES TO THE BEGINNING Or THE LOOP,
THE LEADER COOE C~51), PLUS THE INCREMENT, IS EQUAL IN VALUE
(352) TO THE DATA PLACED IN R2 DURING THE tNITIALI~ATION,
THEREFORE, L£AOER CODE HAS NO £FrECT ON THE LOADER PROGR.M.
tACH TIMt ~EAOER COOE IS READ THE PROCESSO~ ExeCUTES THE SAM£
~OOP AND T~E PROGRAM REM.INS UNMODIFIED,
THE PlRST eOOE
AFTER THE LEADER CODE (15) REP~ACES THE DATA TO BE ~OAOEO
INTO R2. THIS IS ADDEO TO THE INDtx VALUE (114~0) AND T~E
RESULT POINTS TO THE rlRST LOCATION OF T~E PROGR.M TO BE LOADED
(17416). THE INC INSTRUCTION WHIOH OPERATES ON THE
DATA FOR R2 ~UTS DATA BYTES IN SEQUENTIAL LOCATIONS, AND
REQUI~ES THAT THE VALUE OF THE LEADER COOE AND THE OrFSET BE
ONE-~ESS THAN THE VALUE OESIREO IN R2 SINCE TH~ INCREMENT
OCCyRS BErORE THE DATA IS LOADED.
THE BOOT OVER~AY IS ACCOMPLISHED BY LOADING SEQUENTI.L
~OCATIONS FROM THE ST.RT OF T~E PROGRAM UP TO THE BEGINN%NG OF
~OAD~R <I.E. FROM 11416 TO 17144) WHERE IT BEGINS THE OVERLAY.
THE SECTION ~OADEO JUST BEFORE THE BOOT LOADER IN CORE IS
SUBROUTINE WHICH WI~L RESTORE THE LOADER TO ITS INITIA~ rORM

A
AND "JUMP TO THE BEGINNING OF THE LOADED PROGRAM.
THIS PORTI~N OF tHE PROGRAM IS ENTERED BY THE OVER~AY'S
CHANGING OF THE BRANCH INSTRUCTION AT THE END OF THE
BOOT LOADER (11714) ONC£ THE END OF THE TAPE IS REAO~ED,
THli CAUSES, BRANCH TO THE BEGINNING or THE RESTORE
RouflNE, RATHER T~AN r~E BEGINNING O~ LOAOER. SINCE
THE MAINTENANCE LOADER IS SHORTER THAN THE SPACE AVAILABLE.
THE SECTION BETWEEN THE ENO Or THE MAINTENANCE LOAOER ~NO
THE 8EGINNING Or THE RESTORE ROUTINE IS LOADED WITH 'EROES.
THIS LOAOING Or EXTRA rRAMES ~OLCS TRUE 'OR OTHER SOOT TAPES
WHICH DO NOT USE ENOUGH ~OCATIONS TO ALLOW OONTINUOUS LOADING.
THE-OATA ~OADEO is NOT NECESSAAI~Y ~ERO£S, HOWEVER.
ONCE THE LAST BYTE OF T~E RESTORE ROUTINE IS PLACEO IN THE
CORE LOCATION IMMEDIATELV PRECEDING THE LOADER, THt SOOT
OVERLAY COOE WILL OVERLAY THE rIRST TWO INSTRUCTIONS Or THE

THE BOOT

MAINOEC-11-09EA
PAGE 7
BOOTSTRAP ~O'OER, T~E 1ST INSTRUCTION IS UNC~ANGEO av T~E
OVER~AY, BUT T~E SECOND INSTRUCTION IS CHANGED TO 313 TO
MAKE THE ADDRtSS OISP~ACEMENT, ONCE INCREMENTEO, POINT TO
~OCATION 117'.,
T~£ NEXT BYTE REAO IS T~ERErOAE
PLAC~D INTO T~£ ~OWER BYTE or T~E BRANCH INSTRUCTION.
BY CHANGING 'HE orrSET IN T~lS BRANCH INSTRUCTION, THE LOAOER
WILL BRANC~ ~O T~[ STAR' or THE RESTORE eOOE WHICH WIL~
RESTORE THE eOOTSTR.P LOADER TO ITS ORIGINAL CONOITION BY
RESTORING THE CONTENTS or LOCATIONS 177'2 ANO 17774 TO 351
ANO-'65 RESPECTIVELY ANO THEN JUMP TO 17416 ANO HALT CAT
THE aEGI~NING or T~E MAINT LOAOER),
9.0

PRO;RAM OESCRIPTION

9.1

JNPIJT fORMAT
F'RAME

-1
-2
-3

001
000

ByTE COUNT • 1.0WER ORDER
BYTE COUNT .. HIGHER ORDER
.5
LOAO AOORESS • LOWER ORDER
LOAD ADDRESS • HIGHER OROER
-6
DATA
PI..ACE;O
HERE
CKSM • LAST rRAME CONTAINS THE CHECKSUM
•4

Ir THE BYTE OOUNT IS EQUAL TO 6, THE LOAO AOO~£SS SPEClrtEO
WILL BE CONSIDERED TO BE THE DESIREO JUMP ADDRESS, It T~rS
ADDRESS IS ODD. T~E LOAOER WI~~ ~ALT,
IF IHE BYTE COUNt IS > 6, OAT A WILL BE LOAOEO INTO MEMORY,
9.2

REGISTERS
CKSM = R0
AOR :; R1
Be
= R2
.....
BYT - iii"
WRD = R4
RET = R,
SP
= R6
PC
= R7

USED TO CALCU~AT[ CHECKSUMS
LOAD ADDRESS
BYTE COUNT
CONTENTS OF' eYiE (A~SO USED FeR OEviCE AORS)
rULI. WORO ADDRESS (rOR ASSEMBLING eYTE COUNT AND LOAD ADDRESS)
RETURN rROH SUBROUTINE POINTER
STACK POINTER (NOT USEO)
PROGRAM COUNTER

THE OEVICE AOORESS IS ~E~D IN ~OCATION 1"76. THE OE.VICE
ADO~ESS IS MOVED TO R3 AT THE 9Ec.INNING or THE REAO SUBROUTINE, ONCE A rRAME HAS BEEN REAO, THE OAT A IS STORED
IN THE ~OWER BYTE or R3. T~E CHECKSUM IS CONTAINEO IN T~E
~OWER BYTE or R~~
AT COMPI.ETION or LOAOING, T~E LOWER
eVTE or THE OATA LIGHTS S~OU~O BE lERO, SIGNIrYING
SUCCESSrUL ~OAOING Or THE TAPE,

Maindec-ll-D9EA
Page 8
11.

Maintenance Loader Flowchart

Byte

coun~R2

R2-~R2

A ;-------41

1747¢-')SP(R6)

Set up stack
pointer incase
rror occurs.

(4
frames alread
read)

Read in load
address (next
2 frames)

~Cksum

(R¢)
initialize
checksum

>--Y---~IQ
Load address
Rl to set u
for loading.

Read next
frame (blank)

Read in byte
count (next
frames)

Halt with bad
cksum
displayed

Maindec-ll-D9EA
Page 9
Maintenance loader flowchart continued

ReadTt

Move reader

frame from
paper tape

address~R3

and start

Jump to loadJ

>----.....,;=lII :~~~: ~!g (us e_

addres s }

Move reader
data buffer
content~R3

Return to
begin if
continue is
ressed

Cksum + data
.... cksum

Decrement
byte count

Po.R5
Save PC for
return

Branch to
read
subroutine

R5 +

move return
past the
branch.

R5""" PC
Load
Return PC

PAI-Xll

16144

V01l3

PAGE:

I POP-11 Mol I NTENANCE: ~O'DE:R
COPYRI~HT ~970,

INPUT F'oRMAT
FRAME:

-1

.2
.3
.4
·5
.6

OIGI'T'AL. E:QUIPMEN'I' CORPORATION
11lI1l1
01210
BYTE
BYTE
L.OAO
L.OAO

COUNT • L.OWE:R OROER
COUNT • HI GIoIE:R OROER
AOORESS - LOWER ORDER
ADDRESS - HI GIolER ORDER
CATA
PL.ACE:D

CKSM • L.UT· F'RAME:

co~~:i NS TWE CWECKSUM

I F THE BYTE COUNT IS EQUAL. TO 6. THE L.OAO ACORESS
SPECIF'IED WIL.L BE CONSIDERED TO BE TIolE OESIRED JUMP
AOORESS.
IF' THIS .DDRE:SS is ODD. THE L.OAOER WILL H.LT.
I F' THE BYTE COUNT IS> 6. DATA
,STORAGE REQUIREO '" 84 WOROS.
I

101 I L.L.

BE L.OADEO I NTO MEMORY.

REGISTERS USED

Rl.R2.R:5.R4.R5.R6.R7.

OPERATING I NSTRUCT IONS 1
1. US I NG THE; BOOT L.OADER. L.OAO THE MA 1NT LOADER TAPE:.
2. TIoIE: OEVICE AOORE;;'S USED WILL BE CONTAINED Ir.J 17776. IF' THIS
OEVICE AODRE.,.S IS i!ERO TIolE MAINT LO",OER WIL.L NOT RUN.
:5. PLACE THE MAINT LOAOE:R STARTING AOORESS(17500) IN HIE SWITCH
REG I STER AND PRESS 'LOAO ADDRESS.
• PRI!:SS SURT •
5. CIoIECKSUM IS CONTA I NED I N LOWER BYTE OF R0.
L.OWER ByTE OF' DISPLA of SHOULD EQUAL. i!ERO UPON SUCCESSrUL
LOAO I NG OF TIolE TAPE.
6,
I r THE L.OAOER IoIAL. TS WHEN DONE 1T IS ONLY NECESSARY TO
PRESS CONT I NUE TO READ I N ~DD IT 10NAL. TAPES.
I F' THE L.OAOER HALTS AT TIolE FA I L. ADDRESS C17612). A CIoIEC!<SUH
ERROR 101",$ OCCURRED. MOVE TIolE PA!'ER TAPE BACK TO THE
BEGINNING OF TIoIE CURRENT BL.OCK .ND HIT CONTINUE TO TRY AGAIN.
I

•

01775121
01740121
'!I17774

PAl-XU

017472
~17474

~17476

1il17!)00
017!)11l4
017506
017512
017~14

017516
01.7520
ill 7522
11l17!)24
IH7!)26
017!;J2I
11l175:52
017534
017536
11117540
0175.4
11l175.6
017!;52
1:117554
f1l17!)56
017560
017!)62
017!)64
01757"
017572
017574
017576
0171>00
21171>02
0176,,4
ilJ.7606
017610
01.7~12
017~14

017616
017620

017l!22
017~26

0171>:50
12117(;32
"17634
0176'0
017642
121176.'
121176.6
"176521
017652
017654
017~56

'1003
017476
U7'72
2II1J000121
0001210121
11l0012111l121
012706
1l"512100
2!12711l4
U0705
2100442
e'05303
"01374
010705
(1100436
01071115
11l2l04J4

L.OOPII177,"
L.OAO.114"0
BRNCH·17774

16-NOY·711l

16144

017470

,'"17472
RETURN I
WR011
STRTl,:
BEGIN:

017474

~10Jl.

r.l10705
U0431
110337
11111402
162702
12110705
0021422
010314
010705
000417
110337
005702
211211426
III 114 I1l 1
11I1'l705
I1l 021 4121
00571112
002"04
1121570"
02117:53
11l""0"121
02107:51
110321
000766
01370:5
0"!5213
105713
100376
r;l16J£l3
"6"3"121
0e5302
005725
11110507
11l10711l5
r1100763
1057r11"
11101355

I CHECKSUM I S KEPT IN R0
ILOAr; ADDRESS
I BYTE: COUNT
I CONTENTS 0' BYTE
I FUL.L WORO A!:lORESS
I RETURN FROM SU8ROUT I Nt PO INTER
ISTACK POINTER
,PROGRAM COUNTER

OKSM
.OR
BC
BVT
WRD
RET
SP
PC
I

1111"012100
00001111
000002
11100003
000004
000005
00001116
2!1210011l7

017475
III "ilI.'ll1l.

I1ll7'75

11117776

PAGE 1.1

0
0
IojAL. T
HOY
CL.R
MOY
INIT 1
HOV
BR
DEC
BNE:
MOV
BR
MOV
BR
HOV
MOV
BR
MOVB
MOV
SUB
MOV
BR
MDV
HOY
BR
MOVB
TST
BEQ
MOV
•• L.OADI MOV
BR
TST
BGI!:
TSTB
BEQ
HALT
rAIL I
BR
CONT I
MOVB
BR
REAO.

1ilI1l1ill1l1ll2

JUMPI

MOV
INC
TSTB
BPI.
HOV
AO",
DEC
TST
MOV
!oIOY
BR
TSTB
BNE

117470,SP

I PO I NTER FOR NESTEO RETURN
I LOCH 1ON FOR ASSEHBL Y OF FUL.L WORD
I HAL T H ENO OF LOAD I NG MA I NT LOADER
,SETUP STACK IN CASE

CI<SM
'WROl,.WRO
PC,R[T
RHO
BYT
INIT
PC,
RET
READ
PC.RET
READ
eYT, 'WRD
PC,Rn
REAO
BYT I flWRD1+1
,WRD,BC
'4,BC
PC,RET
READ
BYT ,'WRD
PC,RtT
'tEAD
BYT, "WRD1"'"
BC
JUMP
.WRD, AOR
PC,RET
READ
BC
CONT
CKSM
BEGIN

I LOAD PO! NTER INTO 04
I SETUP RETURN
I R!! AO NEXT FR",,1E
,DECREMENT CHARACTER
I IF NOT FIRST CHARACTER. L.OOP
,REAO NE)!T PRAME
,SETUP RETURN
,REAO IN BYTE COUNT
,SAVE IN WR01 (LOW BYTE)
I SETUP RETURN FROM REAO SUB
IREAO NEXT FRAME (HIGH BYTE)
I MOVE BYTE COUNT TO R2
,SUBTRACT 4 FROM BYTE COUNT
ISETUP R[TURN
• READ 1N L.OAD ADDRESS
IS4VE IN WROl (LOW BYTE)
: SETUP RETURN FROM READ SUB
,REAO NEXT PRAME (H I GH BYTE)
I TEST BVTE COUNT
IBRANCIol IF' NO DATA IN BLOCK
I'STORE L.OAD ADORESS
: SETUP RETURN
I READ NEXT "'RAME
.1 F NOT CHECI(SUM CONT I NUE
I TEST CKSUM TOTAL
I ST APT ANOTHER BLOCK IF' CKSUM OK
,CHECKSUM FAILED
IRE~TART

BEGIN
BVT, (AORI'"
A.L.OAD

I LOAD CHARACTER INTO L.O.D ADDRESS
,CONT I NUE

"1"76'''3
."3

IMOVE DEVICE AODRESS TO R3
I SH,n DEV I ce:
,WAIT rOR DONE

2(":5).BYT
BYT, CKSM
BC
(RET)+
RET, PC
PC,RET
liE "'0
OKSH
FUL-

,HOVE: BYTE TO R3
I ADO BVTE TO CHECKSUM
I DECREMENT BYTE COUNT
IUPDATE NEW PC FOR RETURN
, RETURN
,SETUP R[TURN
• REAO NEXT rRAME
,TEST CHECKSUH
IBR ANCIol I F' NOT i![RO

n3
,-2

PALXl1

YBn

~:. 7e>60

1il06214
1 1lI3011J 2
0rlJ000I!J
1110073 ..

~! 7662
~17664

017666

~lH;7"

017~72

1e-tl/OY-'0

:\,6IU

1-2

Ur:t
Bee
H'1. T
BR
AS I.
MOY
,JUPT

",UH4
U3707
"00"13

PACE

017474

IWj:lO
,+6
BEG I N
,WRO
UIolR01,IIC

JCHECK LOAD 40Dj:lESS
IBRANC~ Ir 1.0.0 AOORESS EVEN
I.OAO ADDRESS ODD
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,JUMP TO

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BEGIN
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2117472
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ERRORS DE HCTEO I 0
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41< CORE USED

SECONOS

111

0
0
0
0
0

1110111352

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0
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,END

177532

1S-t,jOV-H

16: 44

PAGE 2-1

'1.00P-1.0"0+2, LOOP+2
.765, BRNCIol

$TRTl
I LOAD OVER BOOTSTR4P TO CAUSE JUMP TC 17724