;*****************
;Optimized rowread
;*****************
;C prototype: void opt_rowread (unsigned short row);
;
;unsigned char opt_rowread (register unsigned short row asm("%d0"));

; d0.w: keyboard row mask
; Outputs column mask in d0.b
	xdef	opt_rowread
opt_rowread:
	not.w   d0
	andi.w  #$03FF,d0
	move.w  d0,($600018)
	move.w  #23,d0
__rr_loop:
	dbf     d0,__rr_loop
	; Read value and store it in d0
	move.b  ($60001B),d0
	not.b   d0
	rts