csioa.a51

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;*************************************************************************
; An 8051 Based Web Server
; csio.a51: driver code for CS8900A chip located at 7000h
; By Mason Kidd 10/25/01
;*************************************************************************

$NOMOD51
$INCLUDE(reg515.inc)

name		csioa
public		_write_byte, _read_byte, _write_word, _read_wordL, _read_wordH 

sc_csio	SEGMENT	CODE
		RSEG	sc_csio
 		
               USING 0
               
csio_port	EQU	70h
               
; write_byte(io_port = R7, data = R5)
_write_byte:
	push	ACC
	mov	A, R7
	add	A, #csio_port
	mov	DPH, A
	mov	A, R5
	movx	@DPTR, A
	pop	ACC
	ret
	
; read_byte(io_port = R7), value returned in R7
_read_byte:
	push	ACC
	mov	A, R7
	add	A, #csio_port
	mov	DPH, A
	movx	A, @DPTR
	mov	R7, A
	pop	ACC
	ret
	
; write_word(io_port = R7, data = R4R5)
; send the low order byte first(R5)
_write_word:
	push	ACC
	mov	A, R7
	add	A, #csio_port
	mov	DPH, A
	mov	A, R5
	movx	@DPTR, A
	mov	A, R7
	add	A, #csio_port
	inc	A
	mov	DPH, A
	mov	A, R4
	movx	@DPTR, A
	pop	ACC
	ret
	
; read_wordL(io_port = R7) return in R6R7
; read the low order byte first(R7)
_read_wordL:
	push	ACC
	mov	A, R7
	mov	R1, A
	add	A, #csio_port
	mov	DPH, A
	movx	A, @DPTR
	mov	R7, A
	mov	A, R1
	add	A, #csio_port
	inc	A
	mov	DPH, A
	movx	A, @DPTR
	mov	R6, A
	pop	ACC
	ret
	
; read_wordH(io_port = R7) return in R6R7
; read the high order byte first(R6)
_read_wordH:
	push	ACC
	mov	A, R7
	mov	R1, A
	add	A, #csio_port
	inc	A
	mov	DPH, A
	movx	A, @DPTR
	mov	R6, A
	mov	A, R1
	add	A, #csio_port
	mov	DPH, A
	movx	A, @DPTR
	mov	R7, A
	pop	ACC
	ret
	
       end