IBM 5150

LOC OBJ
LINE
SOURCE
F980
5558 W22:
I
RD-H-Bn'
F980 E462
F982 2410
5559
556.
IN
A..,
AL,PORT.C
AL,OIOH
; INPUT DATA BIT
J HASK Off EXTRANEOUS BITS
F984 3AC4
5561 CMP
AL.AH
I SAHE AS BEfORE?
F986 E1F8
5562 LooPE
W22
i LOOP TILL IT CHANGES
F988 A26BOO
5563
"""
LAST_YAL.AL
I UPDATE LAST_YAL WITH NEW VALUE
F98B BODO
5564 MOV
.U,O ; READ TIMER' S COUNTER COHttAND
F980 E643
5565
OUT TIM_cn.AL
;
LATCH COUNTER
F98F 881E6700
5566
HOV BX,EDGE_CNT ; BX GETS LAST EDGE COUNT
F993 E440
5567
IN
AL,TIMERO ;
GET LS BYTE
F995 8AEO
5568 MOV AH,AL
J SAYE IN AH
F997 E440
5569
IN AL,TIMERO ; GET HS BYTE
F999 86C4 5570
XCHG
.U,AH J XCHG AL.AH
F99B 2B08
5571
sue BX,AX J SET ex EQUAL TO HALF BIT PERIOD
F99D ,436700
5572: MOV
EDGE_CNT ,AX
; UPDATE
EDGE COUNT I
F9AO C3
5573
PET
5574
5575
READ.HALF _BIT
ENOP
; ------------- __________ • _______________________________________ _
5576 I PURPOSE
5577 WRITE 1 OR HORE 256 BYTE BLOCKS TO CASSETTE.
5578 THE DATA IS PADDED TO FILL OUT THE LAST 256 BYTE BLOCK.
5579 ; ON ENTRY:
5580 ex POINTS TO MEMORY BUFFER ADDRESS
5581 ; ex CONTAINS NUMBER OF eYTES TO WRITE
5582 I ON EXIT:
5583 ax POINTS 1 BYTE PAST LAST BYTE WRITTEN TO CASSETTE
5584 CX IS ZERO
5585
J --- ------- - - - - - - - - - - ------- - - - - - - -------- ------------- ----- -- - --
F9Al
5586
~ITE_BLOCJ(
ppoe
NEAR
F9Al 53
5587
PUSH OX
F9A2 51
558& PUSH cx
F9A3 E461
5589
IN AL.PORT_B I DISABLE SPEAKER
F9A5 24FO
5590
AND AL.HOT 02H
F9A7 DeDI
5591
OR AL, 01H I ENABLE TIMER
F9A9 E661
5592
OUT PORT_B,AL
F9AB BOM
5593
MOV AL,OB6H I SET UP TIMER -- MODE 3 SQUARE WAVE
F9AD E643 5594
OUT TlM_CTL,AL
F9AF E81600
5595
CALL
BEGIN_OP
START MOTOR AND DELAY
F982 88 ... 004 5596
MOV
AX,lla4
; SET NORMAL BIT SIZE
F9BS E88500
5597 CALL
W31
; SET_TIMER
F9B8 890008
5598
MOV cX,oaOOH I SET CX FOR LEADER BYTE COUNT
' .. 0
5599
W23:
; WRITE
LEADER
F9BB F9 5600
STC J WRITE DNE BITS
F9BC E86800
5601 CALL
WRITE_BIT
F9BF E2FA
5602
LOOP W23
I LOOP 'TIL LEADER IS WRITTEN
F9Cl F8
5603 CLC • WRITE SYNC BIT (0)
F9C2 E86200
5604
CALL
WRITE.BIT
F9C5 59
5605
pop
CX i RESTORE REGS CX.BX
F9C6 58
5606
pop
OX
F9C7 B016
5607
I'IOV
AL,
16H
I ~ITE SYH CHARACTER
F9C9 E84400
5608
56 ••
CALL WRITE_BYTE
J----------------------------------------------------------------
5610 ; PURPOSE
561J i WRITE 1 OR MORE 256 BYTE BLOCKS TO CASSETTE
5612 I ON ENTRY:
5613 BX POINTS TO MEHORY BUFFER ADDRESS
5614 J CONTAINS NUMBER OF BYTES TO WRITE
5615 J ON EXIT:
5616 BX POINTS 1 BYTE PAST LAST BYTE WRITTEN TO CASSETTE
5617 CX IS ZERO
5618 ; ---------------------------------------- ---------------.----- ---
F9CC 5619
WR.BLOCK:
F9CC
C7066900FFFF 5620 MOV CRC.REG,OFFFFH
;
INIT CRC
f902 BAOOOI 5621
MOV DX.256
I FOR 256 BYTES
nos 5622
1<124: ; WR-BLK
F9D5
268A07
F908 E83500
f9DB £302
5623
5624
5625
MOV
CALL
JCXZ
AL,ES:[BXJ
WRITE.BYTE
.2.
I READ BYTE fROM I1EI1
; WRITE
IT TO CASSETTE
I UNLESS CX=O.
ADVANCE PTRS , DEC COUNT
F90D 43 5626
INC ox
; INC BUFFER POINTER
~
F90E
49 5627
OEC CX
I DEC BYTE COUNTER
F90f 5628
W25: ; SKIP-ADV
F9DF 4A 5629 OEC .x ; DEC BLOCK CNT
F9EO 7FF3 5630
.IS
"2'
i LOOP TILL 256 BYTE BLOCK
5631
I
IS ~ITTEN TO TAPE
5632 1-------- - ------- - - - ------ - - - - -- - - - - -- - - ---- ----- ------ ----- -----
5633 I WRITE CRC
5634 WRITE l' S COMPLEMENT OF CRC REG TO CASSETTE
5-106 System BIOS