; pioml.asm
; 8255 assistance

; L. Stewart, February 7, 1983  7:47 PM
; L. Stewart, March 3, 1983  2:33 PM, GetPIOState

$INCLUDE(Lark.d)

CCClock	EQU	010H
CCData	EQU	020H
CCCBar	EQU	0EFH
CCDBar	EQU	0DFH
SynTSN	EQU	002H

C←CODE SEGMENT

C←DATA	SEGMENT

; char vpio[6];
←vpio	LABEL	BYTE
←vpioa	DB	00H
←vpiob	DB	00H
←vpioc	DB	00H

←vapioa	DB	00H
←vapiob	DB	00H
←vapioc	DB	00H

C←DATA	ENDS

ASSUME CS:C←CODE, DS:C←DATA

pioports	LABEL	WORD
	DB	pioa
	DB	0
	DB	piob
	DB	0
	DB	pioc
	DB	0
	DB	apioa
	DB	0
	DB	apiob
	DB	0
	DB	apioc
	DB	0

; PIOOn(bits, port)
←PIOOn	LABEL	NEAR
	MOV	DI,OFFSET ←vpio
	MOV	AL,[DI][BX]
	OR	AL,CL
	JMP	piocom

; PIOOff(bits, port)
←PIOOff	LABEL	NEAR
	MOV	DI,OFFSET ←vpio
	MOV	AL,[DI][BX]
	XOR	CL,0FFH
	AND	AL,CL
	JMP	piocom

; SetPIO(bits, port)
←SetPIO	LABEL	NEAR
	MOV	DI,OFFSET ←vpio
	MOV	AL,CL
	JMP	piocom

piocom:
	MOV	[DI][BX],AL
	MOV	SI,OFFSET pioports
	SAL	BX,1
	MOV	DX,[SI][BX]
	OUT	DX,AL
	RET

; int GetPIO(port)
←GetPIO	PROC
	MOV	SI,OFFSET pioports
	SAL	BX,1
	MOV	DX,[SI][BX]
	XOR	AX,AX
	IN	AL,DX
	MOV	BX,AX
	RET
←GetPIO	ENDP

; Set up codec with time slot word passed in BX
; SetCodec(timeslot)
←SetCodec	PROC	NEAR
	MOV	AL,←vapioa
	AND	AL,CCCBar		; clear clock
	AND	AL,CCDBar		; clear data
	OUT	apioa,AL
	MOV	CX,8
	OR	AL,CCClock		; set clock
	MOV	DL,AL
tsnlow:					; wait for not TSN
	IN	AL,pioc
	TEST	AL,SynTSN
	JNZ	tsnlow
tsnhigh:				; wait for TSN
	IN	AL,pioc
	TEST	AL,SynTSN
	JZ	tsnhigh

tsloop:
	MOV	AL,DL
	OR	BL,BL
	JNS	tsl0
	OR	AL,CCData		; possibly set data
tsl0:
	OUT	apioa,AL
	AND	AL,CCCBar		; clear clock
	OUT	apioa,AL
	SAL	BX,1
	LOOP	tsloop

	AND	AL,CCDBar		; clear data
	OUT	apioa,AL
	MOV	←vapioa,AL
	RET
←SetCodec	ENDP

; returns pointer to core copy of pio state
←GetPIOState	PROC	NEAR
	MOV	BX,OFFSET ←vpio
	RET
←GetPIOState	ENDP

PUBLIC	←vpio
; PUBLIC	←vpioa
; PUBLIC	←vpiob
; PUBLIC	←vpioc
; PUBLIC	←vapioa
; PUBLIC	←vapiob
; PUBLIC	←vapioc
PUBLIC	←PIOOn
PUBLIC	←PIOOff
PUBLIC	←SetPIO
PUBLIC	←GetPIO
PUBLIC	←SetCodec
PUBLIC	←GetPIOState

C←CODE ENDS
	END