COMIO.ASM

	page	,132
	title	COMIO.ASM

;
;   COMIO.ASM
;   COM input/output services
;
;   by Jeff Parsons 31-Jan-1993
;


	include all.inc
	include com.inc


OPEN_DATA

	public	_COMPort
_COMPort    dd	0

CLOSE_DATA


OPEN_CODE

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;   _COMInit
;
;   ENTRY
;	iPort == COM port # to use
;
;   EXIT
;	EAX == TRUE if successful, FALSE if not
;
;   USES
;	Only EAX, ECX, EDX (C standard)
;
	assume	cs:CODE_SEG,ds:DATA_SEG,es:DATA_SEG,ss:DATA_SEG

	public	_COMInit
_COMInit    proc near

	sub	eax,eax			; EAX == FALSE
	mov	edx,[esp+4]		; EDX == COM port # (1 or 2)
	dec	edx			; convert to 0 or 1
	cmp	edx,1			; out of range?
	ja	com_exit		; yup

	mov	ecx,[_pmbZero]
	movzx	edx,[ecx].rb_RS232Base[edx*2]
	or	edx,edx			; port exist?
	jz	short com_exit		; nope
	mov	[_COMPort],edx		; yup, save it

	mov	ecx,BD_9600		; (ecx) = new baud rate
	mov	eax,CLOCK_RATE
	cdq				; (edx:eax) = clock rate
	div	ecx
	mov	ecx,eax			; (ecx) = clock rate / baud rate
;
;   Set divisor-latch access bit (DLAB) in line control reg.
;
	mov	edx,[_COMPort]

	add	dl,COM_IER
	xor	al,al
	out	dx,al
	IODelay
	add	dl,COM_LCR-COM_IER	; (edx) -> LCR
	mov	al,LC_DLAB		; turn on DLAB
	out	dx,al
	IODelay
;
;   Set divisor-latch value.
;   (dx) -> COM_LCR (Line Control Register)
;
	add	dl,COM_DLL-COM_LCR	; (edx) -> LSB of baud latch
;	in	al,dx
;	cmp	al,cl
;	je	short com_lsbdone
;	IODelay
	mov	al,cl			; (al) = divisor latch LSB
	out	dx,al			; set LSB of baud latch
	IODelay

com_lsbdone:
	inc	dx
;	in	al,dx
;	cmp	al,cl
;	je	short com_msbdone
;	IODelay
	mov	al,ch			; (al) = divisor latch MSB
	out	dx,al
	IODelay

com_msbdone:
;
;   State of LCR is same as initcom in IBMBIO. (LCR = 3)
;   (dx) -> COM_DLM
;
	add	dl,COM_LCR-COM_DLM	; (edx) -> LCR
	mov	al,3			; (al) = same mode as in IBMBIO
	out	dx,al
	IODelay
;
;   Enable the FIFO on a 16550A
;
IFDEF LATER
	add	dl,COM_IER - COM_LCR
	mov	al,00000111b
	out	dx,al
	IODelay
	in	al,dx
	IODelay
	test	al,10000000b
	jz	short com_nofifo	; No FIFO
	test	al,01000000b
	jnz	short com_done		; 16550A
com_nofifo:
	xor	al,al			; 16550 or no FIFO
	out	dx,al
ENDIF

com_done:
	mov	eax,TRUE		; return TRUE

com_exit:
	ret

_COMInit    endp


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;   _COMInput
;
;   ENTRY
;	None
;
;   EXIT
;	EAX == character, 0 if none
;
;   USES
;	Only EAX, ECX, EDX (C standard)
;
	assume	cs:CODE_SEG,ds:DATA_SEG,es:DATA_SEG,ss:DATA_SEG

	public	_COMInput
_COMInput   proc near

	sub	eax,eax
	mov	edx,[_COMPort]
	or	edx,edx
	jz	short com_exit

	add	dl,COM_LSR
com_wait:
	in	al,dx
	IODelay
	and	al,1
	jz	short com_exit

	sub	dl,COM_LSR-COM_DAT
	in	al,dx
	and	al,7Fh

com_exit:
	ret

_COMInput   endp


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;
;   _COMOutput
;
;   ENTRY
;	chOut == character to output
;
;   EXIT
;	EAX == TRUE if successful, FALSE if not
;
;   USES
;	Only EAX, ECX, EDX (C standard)
;
	assume	cs:CODE_SEG,ds:DATA_SEG,es:DATA_SEG,ss:DATA_SEG

	public	_COMOutput
_COMOutput  proc near

	mov	edx,[_COMPort]
	or	edx,edx
	jz	short com_exit

	add	dl,COM_LSR
com_wait:
	in	al,dx
	IODelay
	test	al,020h
	jz	short com_wait

	sub	dl,COM_LSR-COM_DAT
	mov	al,[esp+4]
	out	dx,al

com_exit:
	ret

_COMOutput  endp


CLOSE_CODE


	end