The keyboard is read by outputting a row on the address line A8 to A15 and reading the KBD register in BLINK. The keyboard matrix looks like this:
------------------------------------------------------------------------- | D7 D6 D5 D4 D3 D2 D1 D0 ------------------------------------------------------------------------- A15 (#7) | RSH SQR ESC INDEX CAPS . / £ A14 (#6) | HELP LSH TAB DIA MENU , ; ' A13 (#5) | [ SPACE 1 Q A Z L 0 A12 (#4) | ] LFT 2 W S X M P A11 (#3) | - RGT 3 E D C K 9 A10 (#2) | = DWN 4 R F V J O A9 (#1) | \ UP 5 T G B U I A8 (#0) | DEL ENTER 6 Y H N 7 8 -------------------------------------------------------------------------
DIA <DIAMOND> key
SQR <SQUARE> key
LSH Left <SHIFT> key
RSH Right <SHIFT> key
LFT <LEFT> arrow key
RGT <RIGHT> arrow key
DWN <DOWN> arrow key
UP <UP> arror key
The keyboard can be read directly using a piece of code like below, although note that while reading the keyboard, BLINK will stop the processor for up to 40us:
ld c, $B2 ; I/O port $B2
ld b, row ; one row of A15-8
in a, (c) ; get column data in A
To check for the escape key being pressed.
ld c, $B2
ld b, @01111111 ;Detect keys in matrix top row.
in a, (c)
cp @11011111 ;Bit pattern returned if only the escape key is pressed.
If KWAIT (in INT) is set then performing a key read read will send the machine into Snooze state. When a key press is made the machine will wake up and if KEY (in INT) is set then a keyboard interrupt will occur.