;

      TITLE ZMR4-1.Z80 - 01/01/88 - ZMD I/O Overlay for TRS-80 MODEL IV
;				    Copyrighted (c) 1987, 1988
;				    Robert W. Kramer III

	PAGE
;-									 -;
;                         Update History                                  ;
;                                                                         ;
;    Date	Release			     Comments                     ;
;  --------	-------	  ----------------------------------------------  ;
;                                                                         ;
;  01/01/88	v1.00	- Initial version				  ;
;-                                                                       -;

;
MSPORT	EQU	0E8H		; Modem status port
USPORT	EQU	0EAH		; UART status port
DPORT	EQU	0EBH		; Data holding register I/O
MSNDRDY EQU	040H		; Modem send ready bit      1=true
MRCVRDY EQU	080H		; Modem receive ready bit   1=true
CDOK	EQU	020H		; Carrier detect bit        1=true

;
;-------------------------------------------------------------------------;
; Input/Output Jump Table						  |
;-------------------------------------------------------------------------;
;

	ORG	0580H		; Start after configuration table

	JP	0000H		; See CONOUT.INF
	JP	INIT		; Initialization routine
	JP	UNINIT		; Unititialize routine
	JP	SNDCHR		; Send character
	JP	CARCHK		; Test for carrier
	JP	GETCHR		; Get character from modem
	JP	RCVRDY		; Check receive ready
	JP	SNDRDY		; Check send ready

;
;-------------------------------------------------------------------------;
; System startup inititialization routine				  |
;-------------------------------------------------------------------------;

INIT:	RET

;
;-------------------------------------------------------------------------;
; System exit unititialization routine					  |
;-------------------------------------------------------------------------;

UNINIT:	RET

;
;-------------------------------------------------------------------------;
; Send character out modem						  |
;-------------------------------------------------------------------------;

SNDCHR:	POP	AF		; Get character from stack
	OUT	(DPORT),A	; Sendit
	RET

;
;-------------------------------------------------------------------------;
; Check for carrier							  |
;-------------------------------------------------------------------------;

CARCHK:	IN	A,(MSPORT)	; Read modem status port
	AND	CDOK		; Mask carrier detect
	RET

;
;-------------------------------------------------------------------------;
; Get character from modem						  |
;-------------------------------------------------------------------------;

GETCHR:	IN	A,(DPORT)	; Read the data port
	RET

;
;-------------------------------------------------------------------------;
; Check modem receive ready						  |
;-------------------------------------------------------------------------;

RCVRDY:	IN	A,(USPORT)	; Read UART status port
	AND	MRCVRDY		; Mask receive ready
	CP	MRCVRDY		; Z = ready
	RET

;
;-------------------------------------------------------------------------;
; Check modem send ready						  |
;-------------------------------------------------------------------------;

SNDRDY:	IN	A,(USPORT)	; Read UART status port
	AND	MSNDRDY		; Mask crap
	CP	MSNDRDY		; Z = ready
	RET


	END