MCLZ8 - Fetch_opcode() is wrongly used to retrieve immediate values, displacements or offsets in an instruction.

[hlide]

This function is called too often wrongly to retrieve immediate values, displacements or offsets in an instruction. You should use a MEM_READ_BYTE (3 T-states) and not an OPCODE_READ_M1 (4 T-states) for them!

Projects/MCLZ8/Code/Standard_Z80/MCLZ8.ino

Line 629 in 26b2c27

uint8_t Fetch_opcode() {

There is no M1 = 0 and no refresh when retrieving immediate values, displacements or offsets in an instruction!

See here a complex example here: https://floooh.github.io/2021/12/06/z80-instruction-timing.html#dd-and-fd-prefixes. Be aware the table are showing steps per half-cycle (half T-state) so a MEM_READ_BYTE would be 6 rows for 3 T-states.

[MicroCoreLabs]

Thank you for finding this bug! Code updated.