I am beginning work on a Zilog Z80 emulator which runs on an Teensy 4.1 that can be used as a drop-in replacement for the original Z80. I recently bought a TRS-80 Model III to test this with…

The first step is to figure out which Z80 IO’s will map to the Teensy 4.1 and also any buffers that are needed to translate between 3.3V and 5V. I found that four buffers will do the trick with one of them being used to latch the lower eight Z80 address signals.

Many of the IOs will be the same as the MCL86+ which is my 8088 emulator, which will save a lot of time!

The board is now being built, so I have time to write the actual Z80 emulator code. I will start with the bus interface and then expand to support the multiple levels of opcode decode and then the actual opcodes themselves!