;
;	Subroutine GIO
;
;	Purpose - To allow direct I/O access to general purpose
;		communications port.
;
;	Calling sequence - CALL GIO (BUFFER, N_BYTES)
;
;	Where :
;
;	BUFFER - Is the address of the start of the data buffer.
;		 Comes in in H & L regs.
;
;	N_BYTES - Is the address of the number of bytes to be transferred.
;		  Comes in in D & E regs.
;
	entry	gio
	.radix	16
;
;	Conditional assembly parameters.
;
true	equ	-1
false	equ	not true
gport	equ	false		; Standard VT-180 General Purpose port.
				; Does not exist on VT-180 with
				; Selanar graphics
pport	equ	false		; Standard VT-180 PTP: port.
				; Communications port.
tport	equ	true		; Standard VT-180 LST: port. G.P. port on
				; VT-180 with Selanar graphics.
lport	equ	false		; Generic CP/M LST: port
;
;	I/O equates.
;
qpbaud	equ	90		; Baud rate gen addr. (Printer & G.P.)
gp300	equ	12		; 300 baud
gp1200	equ	22		; 1200 baud
gp4800	equ	36		; 4800 baud
gp9600	equ	3F		; 9600 baud

baud	equ	gp9600		; Adjust baud rate here as req'd

ucout	equ	0F738		; UC1: output s/r
t@uc1cb	equ	0F53E		; UC1: I/O control block
ppout	equ	0F754		; PTP: output s/r
t@ptrcb	equ	0F536		; PTP: I/O control block
ttout	equ	0F6E0		; TTY: output s/r
t@ttycb	equ	0F4E8		; TTY: I/O control block
bdos	equ	5		; CP/M bdos entry
lfunc	equ	5		; LST: function code
;
;	Main routine starts here.
;
;	Set up the ports.
;
gio:
	if	not lport
	lda	init		; Check to see if baud init req'd
	ora	a
	jnz	noinit
	inr	a		; Clear init flag
	sta	init
	mvi	a, baud		; Set baud rate
	out	qpbaud
	xra	a		; Set for XON/XOFF
	endif

	if	gport
	sta	t@uc1cb+1	; UC1: port
	endif

	if	pport
	sta	t@ptrcb+1	; PTP: port
	endif

	if	tport
	sta	t@ttycb+1	; TTY: port
	endif
;
;	Send the string out.
;
noinit:
	xchg			; Get number of bytes from D & E
	mov	a, m		; 
	xchg			; Restore buffer addr. to H & L
loop:
	if	gport or pport or tport
	mov	c, m		; Get a character
	endif

	if	lport
	mov	e, m		; Get a character
	endif

	push	psw		; Save context
	push	h

	if	gport
	call	ucout		; Send it out UC1: port.
	endif

	if	pport
	call	ppout		; Send it out PTP: port.
	endif

	if	tport
	call	ttout		; Send it out TTY: port.
	endif

	if	lport
	mvi	c, lfunc	; Send it out LST: port.
	call	bdos
	endif

	pop	h
	pop	psw
	inx	h		; Bump buffer addr
	dcr	a		; Bump char count
	jnz	loop		; Loop til buffer empty

	ret

	if	not lport
init:	db	0		; Initialization flag
	endif

	end