Re: Sandy Keyboard Interface, appeal
Posted: Sun Mar 12, 2023 12:05 pm
Ok, so if I am right that only pins 13 to 18 need to be checked to find out if they are output or input, then this is what I have:
Pin
13 - Goes to the base of a BC238B Transistor (so is an Output).
14 - Goes to the EXTINT connection on the expansion slot connector (so is an Output).
15 - Goes to pin 18 of a 74LS244, which is an output on the 74LS244 (so is an Input).
16 - Goes to pin 19 of the same 74LS244, which is 'enable' (so is an Output).
17 - Goes to pin 9 of a 74HCT164, which is 'clear' (so is an Output).
18 - Goes to pin 20 of the 27128 EPROM, which is 'enable' (so is an Output).
Does that all look correct?
Pin
13 - Goes to the base of a BC238B Transistor (so is an Output).
14 - Goes to the EXTINT connection on the expansion slot connector (so is an Output).
15 - Goes to pin 18 of a 74LS244, which is an output on the 74LS244 (so is an Input).
16 - Goes to pin 19 of the same 74LS244, which is 'enable' (so is an Output).
17 - Goes to pin 9 of a 74HCT164, which is 'clear' (so is an Output).
18 - Goes to pin 20 of the 27128 EPROM, which is 'enable' (so is an Output).
Does that all look correct?