Z80 Routines:Input:GetCSC

This is a replacement for the GetCSC routine. Its returns are exactly the same. You need to have a variable called lastKey so keys won't repeat. Unless you want that. Feel free to add versions with fun stuff like controlled repeating.

;====== GetCSC clone ===========================================================
; This routine is a replacement for the GetCSC bcall.  Its returns are the same.
; Inputs:
;  - None
; Outputs:
;  - A: Keycode
; Destroys:
;  - AF, BC

; To do: Add debouncing

GetCloneSC:
;	push bc			; uncomment for preserving bc
	ld	c, 0BFh
	ld	b, 7
getCSCloop:
	ld	a, c
	out	(1), a
	nop
	nop
	nop
	rrca
	ld	c, a
	in	a, (1)
	cp	0ffh
	jr	nz, getCSCgotCSC
	djnz	getCSCloop
	xor	a
	ld	(lastKey), a
	ret
getCSCgotCSC:
	dec	b
	ld	c, b
	call	getResetBit
	ld	a, b
	sla	c
	sla	c
	sla	c
	add	a, c
	ld	b, a		; This dance ensures that
	ld	a, (lastKey)	; the keycode is returned in A
	ld	c, a
	ld	a, b
	cp	c
	ld	(lastKey), a
	jr	nz, getCSCgoodCSC
	xor	a
getCSCgoodCSC:
;	pop bc
	ret
			
getResetBit:
	cp	$FF
	ret	z
	ld	b, 0
getResetBitLoop:
	rrca
	inc	b
	jr	c, getResetBitLoop
	ret

Alternative Version

This has debouncing?

;Getcsc replacement by James Montelongo 
; Outputs:
;  - A: Keycode
; Destroys:
;  - AF
gsGetK:
gsGetCSC:
	push hl
	push de
	push bc
	ld e,$fe		;frist group
	ld c,$01		;key port
	ld l,0		;l holds key pressed
cscloop:
	ld a,$ff		;For some reason emulator really wants it in the loop
	out (1),a		;reset keyport
	ld h,$fe
	out (c),e		;set keygroup
	ld b,8		;loop, Delay needed when work with key driver
	in a,(c)		;read key
cscbit:
	inc l			;inc to get key pressed
	rra 			; if key pressed done
	jp nc,donecsc
	rlc h
	djnz cscbit 	;loop 8
	rlc e			;next key group
	jp m,cscloop	;if bit 7 set loop
	ld l,0		;if no key pressed 0
donecsc:
	ld a,$ff
	out (1),a
	ld a,e
	cpl
	out (1),a
	nop
	nop
	in a,(1)
	inc a
	jp z,nootherkeypressed
	ld l,0
nootherkeypressed:
	ld a,$ff
	out (1),a
	nop
	ld a,e
	out (1),a
	nop
	nop
	in a,(1)
	cp h
	jr z,only1key
	ld l,0
only1key:
	ld a,l		;
	or a
	ld (gs_keymem),a
	pop bc
	pop de
	pop hl
	ret