Adding I/O to the KIM-1

By Bob Applegate

Adding I/O devices that don’t need much address space. On the KIM-1, the space from 1400-17FF is grouped into the K0 block but only 17xx are used, leaving 1400-16FF open for use. To decode that range into four blocks of 256 bytes is easy using a single chip and a few signals from the KIM Clone expansion bus:

Everyone has a 74LS138 in their parts collection, so just connect a few signals from the expansion bus and use one of the three signals from the 138 to decode which block you want to use. Use the A0-A7 address lines to decode into smaller pieces.