;                 CRTLOOP.Z80




;	ROUTINE TO TEST CRT PORTS
; VERSION 1.1 12-30-82
;
;	  ORG=100H  & 8080 FORMAT
;
CRTS	EQU	0F9H	;HOST SYSTEM KEYBOARD STATUS PORT
CRTIN	EQU	0FAH	;HOST SYSTEM KEYBOARD DATA PORT
CRTO	EQU	0F0H	;VDB-A STATUS OUT/ DATA INPUT PORT
CRTIN2	EQU	0F2H	;VDB-A KEYBOARD DATA PORT
CRTS2	EQU	0F1H	;VDB-A KEYBOARD STATUS PORT
;
ORG	100H
;
START:	IN	A,(CRTS)	;CHECK STATUS OF HOST KEYBOARD
	RLA			;ROTATE TO CARRY
	JP	C,CRT1		;NO-CONTINUE	
	IN	A,(CRTS2)	;CHECK VDB-A KEYBOARD STATUS
	RLA
	JP	NC,START	;NO DATA - START OVER
	IN	A,(CRTIN2)	;YES - GET DATA
	JP	CTLC
CRT1:	IN	A,(CRTIN)	;YES-GET DATA
CTLC:	CP	3		;CTL-C CHECK
	JP	Z,0		;REBOOT TO CP/M
	LD	C,A		;TEMP STORE
CRTOUT:	IN	A,(CRTO)	;CHECK STATUS
	RLA			;ROTATE TO CARRY
	JP	C,CRTOUT	;NO-TRY AGAIN
	LD	A,C		;GET DATA
	OUT	(CRTO),A	;SEND DATA
	LD	A,0		;FOR NEATNESS
	JP	START		;LOOP
END