IBM 5150 Hardware Reference Manual page 262

lOC OBJ LINE SOURCE
F8es
5043
tIDTOR_ON PROC NEAR
5044
j----------------.. ---------------­
5045
j
PURPOSE:
5046
,
TO TURN ON CASSETTE MOTOR
5047
1----­ --­ --­ -­ -­ -­ -­ -­ --­ -­ -­ --­ -_ ...
Fee5 [461
5048
IH
AL,PORT_B jREAD CASSETTE OUTPUT
F887 t4F7 5049
AHIJ AL.NOl OSH
; ClEAR BIT TO TURN ON MOTOR
~
F889 £661 5050 W3:
OUT PORT.B.AL
;WRITE IT OUT
FeSB 2AE4
5051
SUB
AH,AH
;ClEAR AH
F88D C3 S05Z
RET
5053 HOTDR.ON ENOP
5054
F...
5055
MOTOR.OfF PROC HEAR
5056
i ............... -­ --­ -­ -­ -­ -----.---­ ----­ ----­
5057 ; PURPOSE:
5058
5059
•
TO TURN CASSETTE MOTOR OFF
1------------------------. . -----------. . .
'88£ E461 5060 IH At.PORT_B ;READ CASSETTE OUTPUT
f890
oeoe
5061
OR At,.oeH ; SET BIT TO TURN OF f
F892 ESF5 5062
JHP
WJ
;WRITE IT, CLEAR ERROR, RETURN
5063
tIOTOR_OFF ENDP
Fa..
5064 READ.BLOCK PROe:
NEAR
5065
;
-----
------
--
------
--.-
--
---
­
----
----------­
5066 ; PURPOSE:
5067
I
TO READ 1 OR MORE 256 BYTE BLOCKS FROI1 CAsSEnE
5068
5069 I ON ENTRY:
5070 ES IS SEGMENT FOR MEMORY BUFFER (FOR COMPACT CODE)
5071
i
ex POINTS TO START OF MEMORY BUFFER
5012
I
CX COt~TAINS NUMBER OF BYTES TO READ
5073 f ON EXIT:
5074 ex POINTS 1 BYTE PAST LAST BYTE PUT IN MEM
5075 CX CONTAINS DECREMENTED BYTE COUNT
5076 ox CONTAINS NUMBER OF BYTES ACTUALLY READ
5077
5078
•
CAR~Y flAG IS CLEAR IF NO ERROR DETECTED
~
5079 CARRY flAG IS SET IF CRC ERROR DETECTED
5080
j - - - - - - - - - - - - - - - - - - - - - - - - - - - - - _ .. _ - - - - - - - - - - - ­
F894 53 5081
PUSH BX
;SAVE BX
F895 51 5082
PUSH CX
;SAVE CX
F896 56 5083
PUSH
51 ; SAVE 51
F897 BE0700 5084
HOV 51. 7
; SET UP RETRY COUNT FOR LEADER
F89A Eet201 5085 CALl. BEGItCOP ; BEGIN By STARTING MOTOR
F89D 5086 W4: ; SEARCH FOR LEADER
F89D E462 50S7
IN Al,PORT.C
;GET INTIAL VALUE
F89F 2410
50S8
ANO
AL.OIOH ;MASK OFF EXTRANEOUS BITS
F8Al A26BOO
50S9 HOV LAST.VAL,AL ;SAVE IN Lot lAST.VAL
F8A4 BA7A3F 5090
MOV
DX,16250 ; I OF TRANSITIONS TO LOOK FOR
5091
F8A7 5092 W5:
j
WAIT.FOR.EDGE
F8A7 F606710080 5093 TEST
BIOS.BREAK. 80H
; CHECK FOR BREAK KEY
FSAt 7403
SO"
JZ W. I JUMP IF NO BREAK KEY
F8AE E98AOO 5095
JHP W17
~ JUMP IF BREAK KEY HIT
FS81 4A
SO"
5097
..
,
DEC
ox
F882 7503 5098
JHZ
W7 I JUMP IF BEGINNING OF LEADER
F8B4 E98400 5099
JHP W17
; JUMP IF NO LHDER FOUND
5100
F887 E8C600 5101 1017: CALL
READ.HAlF.BIT
;IGNORE FIRST EDGE
FSBA BEB
5102 JCXZ WS
; JUMP IF NO EDGE DETECTED
F8BC BA7803 5103
I10V OX.0378H
; CHECK FOR HALF BITS
F8BF B90002 5104
MOV
CX.ZOOH .MUST HAVE AT LEAST THIS MANY ONE SIZE
5105 • PULSES BEFORE CHECKNG FOR SYNC BIT (0)
F8C! E421
5106
IH AL. 021H
• INTERRUPT MASK REGISTER
Fac4 OC01 5107
OR AL.I
; DISABLE TIMER INTERRUPTS
~
f8C6 E621
5108
OUT
021H. AL
Feea
5109
1.18:
; SEARCH-LOR
F8C8 F6Q6710080 5110
TEST BIOS_BREAK, 80H
; CHECK FOR BREAK KEY
F8CD 756C 5111 JNZ
W17
; JlJ:1P IF BREAK KEY HIT
FeCF 51 5112 PUSH
CX
,SAVE REG CX
F800 ESAOOO 5113 CALL PEAD.HALF_BIT ;GET PULSE WIDTH
F6D3 OBC9 5114
OR
CX. cx ; CHECK FOR TRANSITION
F8D5 59 5115
POP CX ,RESTORE ONE BIT COUNTER
F806 74CS
5116
JZ
"4
1 JUMP IF NO TRANSITION
F8D8 3B03 5117
CHP
OX,BX ;CHECK PULSE WIDTH
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