How to specify output (or input) port?

[Thomas R Consi]

I just got my Relay Computer up and running and am happily learning how to program it. While running the counter program given in the video I noticed that only output 0 is accessed. There is no obvious way from the OUT instruction that I could see to specify which output port to use. How do you specify which output or input port to use in a program?

Thanks! Tom

P.S. The printed circuit board was excellent and the computer went together without a hitch. Kudos to Joe on an outstanding design!

[Joe Allen]

There is only a single port, but it is four bits wide. So, for example, if you write 9 (binary 1001) to the port, bit 0 and bit 3 of it will turn on, and bits 1 and 2 will turn off.

You can also send characters to the console serial port with the OUTC instruction.

[Thomas R Consi]

Got it. Thanks Joe,

Tom