Programming:Keyboard scanning

Hardware scancode table

Bit: Line	7	6	5	4	3	2	1	0
&40	F Dot	ENTER	F3	F6	F9	CURDOWN	CURRIGHT	CURUP
&41	F0	F2	F1	F5	F8	F7	COPY	CURLEFT
&42	CONTROL	\	SHIFT	F4	]	RETURN	[	CLR
&43	.	/	:	;	P	@	-	^
&44	,	M	K	L	I	O	9	0
&45	SPACE	N	J	H	Y	U	7	8
&46	V	B	F	G	T	R	5	6
&47	X	C	D	S	W	E	3	4
&48	Z	CAPSLOCK	A	TAB	Q	ESC	2	1
&49	DEL	-	-	-	-	-	-	-

One line scanning routine

This is a routine which scans one line of the keyboard directly. It is approximately 8% faster then the firmware routine and doesn't enable interrupts.

Input: A = line (&40 - &49)

Output: A = hardware keyboard value

Destroyed: BC

ld a, line	;use the value from the table above
ld bc, &F6C0
out (c), c
ld bc, &F40E
out (c), c
ld bc, &F792
out (c), c
ld b, &F6
out (c), a
ld b, &F4
in a, (c)
ld bc, &F782
out (c), c
ld bc, &F600
out (c), c

Now check for the value from the table e.g. with 'bit x,A' and a condition e.g. 'jp z,xxxx' or 'call z,xxxx'

Please note:

• Bit = 0: Key is pressed
• Bit = 1: Key is not pressed

Complete keyboard scanning routine

This routine scans the complete keyboard and writes all key status bits in a map.

keymap  ds 10  ;map with 10*8 = 80 key status bits (bit=0 key is pressed)

keyscan di              ;1 ##%%## C P C   VERSION ##%%##
        ld hl,keymap    ;3
        ld bc,#f782     ;3
        out (c),c       ;4
        ld bc,#f40e     ;3
        ld e,b          ;1
        out (c),c       ;4
        ld bc,#f6c0     ;3
        ld d,b          ;1
        out (c),c       ;4
        ld c,0          ;2
        out (c),c       ;4
        ld bc,#f792     ;3
        out (c),c       ;4
        ld a,#40        ;2
        ld c,#4a        ;2 44
loop    ld b,d          ;1
        out (c),a       ;4 select line
        ld b,e          ;1
        ini             ;5 read bits and write into KEYMAP
        inc a           ;1
        cp c            ;1
        jr c,loop       ;2/3 9*16+1*15=159
        ld bc,#f782     ;3
        out (c),c       ;4
        ei              ;1 8 =211 microseconds
        ret