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;----- DETERMINE MEMORY SIZE AND FILL MEMORY WITH DATA
;----- WRAP DMA CHANNELS ADDRESS AND COUNT REGISTERS
SOURCE
(BIOS FOR THE IBM PERSONAL COMPUTER XTl
11/08/82
5-117
<><> <><><><> <> <><> <> <> <>
<><><>CHECKPO I NT 3<><><>
WRAP DMA REG
SEND-MASTER CLEAR TO DMA
SET CNT OF 64K FOR REFRESH
SET MODE FOR CHANNEL I
SET MODE FOR CHANNEL 3
SET UP ABSO
INTO DS AND ES
SET INITIAL TIMER CNT TO 0
GET DMA STATUS
1ST I MER REQUEST THERE?
(IT SHOULD'T BEl
HALT SYS. (HOT T I MER
I OUTPUT)
SET MODE FOR CHANNEL 2
DELA Y FOR T I MER
WR I TE PATTERN FF TO ALL REGS
SAVE PATTERN FOR COMPARE
SETUP LOOP CNT
SETUP I/O PORT ADDR OF REG
WRITE PATTERN TO REG, LSB
SATISIFY 8231
I/O TIMINGS
MSB OF 16 BIT REG
AL TO ANOTHER PAT BEFORE RD
READ 16-BIT DMA CH REG, LSB
SAVE LSB OF 16-BIT REG
READ MSB OF DMA CH REG
PATTERN READ AS WR I TTEN?
YES -
CHECK NEXT REG
NO - HALT THE SYSTEM
NXT DMA CH
SET-I/O-PORT TO NEXT CH REG
WR I TE PATTERN TO NEXT REG
SET PATTERN TO 0
WR I TE TO CHANNEL REGS
YES -
SEE IF ALL BITS GO OFF
TIMERI BITS OFF
READ TIMER I
COUNT
ALL BITS ON IN TIMER
TlMERI BITS ON
TI MER I
FA I CURE, HALT SYS
TI MER 1 B ITS OFF
SET T I MER
I-CNT
TIMERI BITS ON
LATCH 1'1 MER-l
COUNT
TIMER LOOP
LA TCH-T I MER
I COUNT
ENABLE DMA CH 0
START TIMER
I
SET DMA MODE,CH O,RD. ,AUOTINT
WR I TE DMA MODE REG
ENABLE DMA CONTROLLER
SET COUNT HI GH=OO
SETUP DMA COMMAND REG
READ T I MER
I COUNT
WRAP DMA REG
TIMER LOOP
HALT SYSTEM
; ENABLE I/O EXPANSION BOX
DX
Cl1
AL
C16
AL,BL
CX,CX
TIMER+ I ,AL
AL,CL
TlMER+ 1 ,AL
DX,0213H
AL,O IH
DX,AL
AL,40H
T I MER+3, AL
AL,40H
T I MER+3, AL
BL,OFFH
CI3
AL, T IMER+ I
BL,AL
C12
AL, TIMER+ I
BL,AL
CI5
CI4
AL,OFFH
BL,AL
BH,AL
CX,8
DX,DMA
DX,AL
AX
DX,AL
AL,O IH
AL,DX
AH,AL
AL,DX
BX,AX
CI8
AL,03H
PORT_A,AL
DMA+ODH,AL
AL,42H
DMA+OBH,AL
AL,43H
DMA+OBH, AL
BX, OAT A WORD [OFFSET RESET FLAG]
,
SAVE 'RESET FLAG'
IN BX
cX,2000R
-SET FOR
16K WORDS
-
BX,1234H
WARM START?
CLR STG
SP,OFFSET C2
STGTST CNT
HOW BIG
STORAGE OK, DE TERM I NE SIZE
BL,AL
SAVE FAILING BIT PATTERN
AL,04H
<><><><><><><><><><><><>
PORT A, AL
<><><>CHECKPO I NT 4<><><>
CX,Ci(
BASE RAM FAILURE - HANG
C24B
FLI PP I NG BETWEEN 04 AND
BL,AL
FAILING BIT PATTERN
C24A
DS,BX
ES,BX
DS: ABSO, ES: ABSO
AL,OFFH
DMA+ I ,AL
AX
DMA+ 1 ,AL
AL,058H
DMA+OBH,AL
AL,O
CH,AL
DMA+8,AL
AX
DMA+ I O,AL
AL,18
TIMER+ I ,AL
AL,4IH
DMA+OBH, AL
AX
AL,DMA+08
AL, 000 I OOOOB
CI8C
PC-XT System BIOS (11/08/82)
INC
LOOP
INC
JZ
MOV
MOV
ASSUME
MOV
OUT
PUSH
OUT
MOV
OUT
MOV
MOV
OUT
PUSH
OUT
MOV
OUT
MOV
OUT
PUSH
IN
AND
JZ
HLT
MOV
OUT
MOV
OUT
MOV
MOV
MOV
MOV
MOV
OUT
PUSH
OUT
MOV
IN
MOV
IN
CMP
JE
HLT
MOV
OUT
CMP
JE
IN
OR
LOOP
HLT
MOV
SUB
OUT
MOV
OUT
MOV
OUT
NOP
NOP
IN
AND
JZ
LOOP
HLT
MOV
OUT
OUT
I NIT I ALI ZE AND START DMA FOR MEMORY REFRESH.
I NIT I AL I ZE T I MER 1 TO REFRESH MEMORY
MOV
MOV
OUT
BASE 16K READ/WRITE STORAGE TEST
DESCR I PT I ON
WR I TE/READ/VER I FY DATA PATTERNS
AA,55,FF,01, AND 00 TO 1ST 32K OF
STORAGE.
VER I FY STORAGE ADDRESSAB I L I TY •
C18:
MOV
MOV
CMP
JE
MOV
JMP
C24:
JE
MOV
MOV
C24A:
OUT
SUB
C24B:
LOOP
XCHG
JMP
CI8C:
C16:
C12:
C15:
Cl1:
C14:
C13:
418
419
420
421
422
423
424
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50 I
502
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510
511
512
513
514
515
516
511
518
519
520
521
522
523
524
525
526
521
528
529
530
LINE
E135 8EDB
E131 8EC3
LOC OBJECT
E 139 BOFF
EI3B E601
E 13D 50
EI3E E601
E 140 B058
EI42 E60B
E144 BOOO
E146 8AE8
E148 E608
E 14A 50
E14B E60A
E14D BO 12
E14F E641
E 151 B041
E 153 E60B
E 155 50
EI56 E408
E 158 2410
E 15A 1401
EI5C F4
EI5D B042
EI5F E60B
E 161 B043
EI63 E60B
E 165 BA 1302
EI68 BOOI
EI6A EE
E 1OE B003
El10 E660
E112 E60D
EI14 BOFF
E 116 8AD8
EI188AF8
EllA B90800
EIID BAOOOO
EI20 EE
EI21
50
EI22 EE
E123 BOOI
E125 EC
E 126 8AEO
E128 EC
E129 3BD8
E12B 140 I
E12D F4
E12E
E12E 42
EI2F E2EF
EI31 FECO
EI33 14EI
E16B 8B1E1204
E 16F B90020
E 112 8 I FB34 12
E116 1416
E118 BCI8EO
El1B E9Fl04
EI1E 1412
EI808AD8
E 182 B004
E 184 E660
EI862BC9
EI88 E2FE
E 18A 86D8
EI8C EBF6
EOE5 8AC 1
EOE1 E641
EOE9
EOE9 B040
EOEB E643
EOED 80FBFF
EOFO 1401
EOF2 E441
EOF4 OAD8
EOF6 E2F I
EOF8 F4
EOF9
EOF9 8AC3
EOFB 2BC9
EOFD E641
EOFF
EOFF B040
EI 0 I E643
El03 90
El04 90
El05 E441
EI0122D8
EI09 1403
E I OB E2F2
EIOD F4
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- Section 1. System Board
- 64/256K System Board
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