title  'Realtime display for VIO/C'

;   This program will use the QT time board to display the real-
;   time date/time on the display driven by a VIO/C video card.
;
clock	equ	080h	; real time clock base port address
screen  equ     0f038h  ;Display address

          org   100h   


     	push psw ! push b ! push d ! push h
time:	lxi	h,hour	; point to hour
	mvi	d,0	; select hour tens digit
	call	ddigit	; read hour tens and units
	inx	h	; step over ":"
	call	ddigit	; read minutes tens and units
	inx	h	; step over ":"
	call	ddigit	; read second tens and units
done:	lxi     d,hour
        lxi     h,screen+9
        call    itgoes
	pop h ! pop d ! pop b ! pop psw
	jmp     100h    ;All done.
itgoes  ldax    d       ;get the characters
        cpi    '$'      ;until exhausted
        rz           
        mov     m,a    
        inx     h
        inx     d
        jmp     itgoes

ddigit:	call	digit	; read and store two digits
digit:	mov	a,d	; move digit select code to a reg.
	call	rdigit	; read a clock digit
	ori	030h	; convert digit to ASCII
	cpi	03fh	; test for blanked leading zero
	jnz	store	; go store digit, if not blanked
	mvi	a,020h	; convert to a blank
store:	mov	m,a	; store the digit in message buffer
	inx	h	; bump message pointer buffer location
	inr	d	; step to next digit
	ani	00fh	; mask off high ASCII nibble
	ret		; return with digit in a reg.

rdigit:	out	clock	; select digit
	mvi	a,0	; ...some delay time for settling
      	dcr	a
	jnz	$-1  
        dcr     a
        jnz     $-1
	in	clock	; read a digit
	ret		; return with digit in a reg.

;
Š; message buffers
;

hour:	db	'xx:'	; the hour...
	db	'xx:'	; the minute...
	db	'xx$'   ; the second...

	end