IBM 5150

LOC OBJ
LINE SOURCE
5635 WHICH IS CHECKED FOR CORRECTNESS WHEN THE BLOCK IS READ
5636
5637
; REG AX IS MODIFIED
1---------------------------------------- -- -- ------------ --- -----
1'9E2 1.16900
F~E5 f700
Fc)E7
1'9E8
F9EA
F9ED
F9EE
F9FI
F9F3
F91'5
F'9F6
F91'9
F91'9
F9FA
F9FD
F9FF
FAOO
FA02
FA04
FA07
fAOA
FAOO
FAaF
FAI0
FAIO
FAll
FA12
50
86£0
£82300
58
£81FOO
OBC9
7507
51
892000
F9
£82AOO
E2FA
59
80BO
£643
860100
£83300
E870FE
28C0
C3
51
50
SAEe
HIlt B108
FA16
FAl6 0005
FA18 9C
FA19 £80BOO
FAit 90
FAID £82400
FA20 FEC9
FAZ2 75F2
1'.24 58
FA25 59
F.6.26 C3
FA27
FA27
88A004
FA2A n03
FAze B85002
FA2F
F All' 50
FA30
FA30
£462
FA32 2420
5636
MOV AX,CRC_REG ; WRITE THE ONE'S COMPLEMENT OF THE
5639
I TWO BYTE CRC TO TAPE
5640
HOT AX ; FOR 1'5 COMPLEMENT
5641
PUSH AX ; SAVE IT
5642
XCHG AH,AL
; WRITE MS BYTE FIRST
5643 I WRITE IT
5644 POP AX
I GET IT BACK
5645
CALL WRITE_BYTE
I NOW WR ITE LS Il YTE
5646 OR CX,CX
;
IS BYTE COUNT EXHAUSTED?
5647
JNZ
WR_BLDCK
;
JUMP IF NOT DONE YET
5646 PUSH CX
, SAVE REG CX
5649
HOV
ex, 32 ; WRITE OUT TRAILER BITS
5650
WZ6: I TRAIL-LOOP
5651
STC
5652 CALL WRITE_BIT
5653 LOOP WZ6
I WRITE UNTIL TRAILER WRInEN
5654
POP CX
; RESTORE REG CX
5655 MOV At. OBOH
I TURN TIMER2 OFF
5656 OUT TIM_CTL, AL
5657
HOV AX, 1
5658
CALL
10131
; SET_TIMER
.. 59
"60
CALL
SUB
MOTOR_OFF
AX,AX
I
TURN MOTOR OF F
I
NO ERRORS REPORTED ON WRITE OP
5661
.. "
RET
,HOP
; FINISHED
5663 ; ----.---------------------------
5664 ; WRITE A BYTE TO CASSEnE.
5665 ; BYTE TO WRITE IS IN REG AL.
5666 ; --------------- - ---- - -----------
5667
WRITE_BYTE MOC NEAR
5666
PUSH CX
J SAVE REGS CX,AX
5669
PUSH AX
5670 MOV CH,Al
i AL::BYTE TO WRITE.
5671
I (MS
BIT WRITTEN FIRST)
5672
HOV
CL.6
; FOR 6 DATA BITS IN BYTE.
5673
I NOTE:
TWO EDGES PER BIT
5674 10127: ; DISASSEHBLE THE DATA BIT
5675
RCL CH,I
; ROTATE MS BIT INTO CARRY
5676
PUSHf
I
SAVE FLAGS.
5677
NOTE:
DATA BIT IS IN CARRY
5678 I WRITE DATA BIT
5679
POPF
I RESTORE CARRY FOR CRC CALC
5680 CALL CRC_GEN ; COMPUTE CRC ON DATA BIT
5661
DEC CL
I
LOOP TILL ALL 6 BITS DONE
5682
JNZ
10127 I JUMP IF NOT DONE YET
5683
POP AX
; RESTORE REGS AX,CX
5664
POP CX
5685
RET
I
WE ARE FINISHED
5686 WRITE_BYTE ENOp
5667 1- -------------- - ----------------------------------------
5686 ; PURPOSE:
5669 TO WRITE A DATA BIT TO CASSETTE
5690 CARRY FLAG CONTAINS DATA BIT
5691 I.E. IF SET DATA BIT IS A ONE
5692 IF CLEAR DATA BIT IS A ZERO
5693
5694
NOTE: TWO EDGES ARE WRITTEN PER BIT
5695 ONE BIT HAS 500 USEC BETWEEN EDGES
5696 FOR A 1000 USEC PERIOD (1 I1IllISEC)
5697
5698
ZERO BIT HAS 250 USEC BETWEEN EDGES
5699 FOR A 500 USEe PERIOD (.5 I1ILLISEC J
5700 I CARRY FLAG IS DATA BIT
5701
1----- ----------------------- ___________________________ _
5702
WRITE_BIT PROC NEAR
5703
J ASSUME IT'S A 'I'
5704
HOV AX. 1184
i SET AX TO NOMINAL ONE SIZE
5705
JC
WZ8
I Jut1P IF ONE BIT
5706
HOV
AX. 592
; NO. SET TO NOMINAL ZERO SIZE
5707 W28:
;
IolRITE-BIT-AX
5706
PUSh AX
; WRITE BIT WITH PERIOD EQ TO VALUE AX
5709
WZ9:
5710
IN AL,PORT_C
I
INPUT TlMER_ 0 OUTPUT
5711
A..,
AL.020H
System BIOS 5-107