A very simple 8-Bit RISC CPU.

In my prior completed project, I built the simplest 4-Bit RISC CPU and computer. It was functional "computer", but very limited without RAM and only 4 bit address and data and with only Add instruction.

https://hackaday.io/project/191290-the-simplest-4-bit-risc-cpu

This project is the expansion of same architecture to 8-Bit RISC which is more functional computer. Address and data expanded to 8 bits, and added instructions and I/O ports and RAM.

Uses only 17 TTL logic chips, 2 EEPROM, and 1 SRAM, and one 555 timer.

Design choices:

Simple 8-Bit RISC CPU.

8-Bit data and 8-Bit Address,

16 Bit instruction, with 8 bit data, 8 bit opcode.

Each instruction executes in 1 clock,

On positive edge of the clock instructions executed.

On negative edge instruction address is incremented.

Instructions Add and Subtract and clear Accumulator.

One 8-Bit output port (for example for 7-segment LED),

and one 8-Bit input.output port.