z80 schematic
Many years ago I had a:
Nicolet NICE in circuit emulator for the Z80
It had only 3 chips. One was a Z80 other was another microprocessor with internal ROM. The third was just buffers.
The idea was that the Z80 could be connected/disconnected from the circuit by the buffers.
As I remember the Z80 was controlled by the other microprocessor. Which also handled the RS232 comm with a terminal emulation on a PC. Real time emulation was possible except for hardware breakpoints.
Text commands from the PC were used to modify memory, load program, step, breakpoints (soft), stop and run.
I might try to find it and post some photos and the numbering of the chips.