A parallel ASCII keyboard is a nice addition to the KIM-1.
Connect to the PIA A of the KIM-1 on the Application connector.
Some keyboards may require a -12 V power supply.
The address 1700 now shows the ASCII keyboard code of (the last) key pressed. The high bit (PB7) is the strobe signal, the other 7 bits the ASCII code.
A program should poll the strobe bit, if activated wait for the strobe bit to be deactivated, and then read the key and return.
Testing for keypressed such as a break test means checking the strobe bit, if activated stop processing, etc..
Code fragments by Hans Otten
PAD * $1700 ; BREAKKEY IN BIT 7 ; SUBROUTINE GET CHARACTER ; GETCH BIT PAD ; PROCEDURE GETCHARACTER ( CHAR ) BPL GETCH ; WAIT FOR STROBE GWAIT BIT PAD ; WAIT FOR END OF STROBE BMI GWAIT ; LDA PAD ; GET CHARACTER RTS ; END GETCHARACTER ; ; example of break test ; SYN BIT PAD ; REPEAT BPL GOON ; WHILE NOT keypressed JMP MONRET ; GOON continue processing