Wozmon (written by Steve Wozniak in 1976) created for the Z80 and Z80-family of peripherals.
The ZMon hex monitor runs in EEPROM (16k) space from address 0x0000. The input buffer is placed in
RAM (48k) at 0x4000 to 0x407F, with one additional word necessary (0x4080, 0x4081). The
stack is initialised to the top of RAM at 0xFFFF.
The monitor uses UART over the SIO peripheral; 8 bits, 1 stop bit, no parity, 9600 baud.
I/O mapping is as follows:
0xC0- SIO (Serial Input/Output)0xE0- CTC (Counter/Timer Circuit)
I use Vasm oldstyle to assemble this project.
Currently, ZMon is 253 bytes in size without I/O initialisation. The additional size to initialise the CTC and SIO are 45 bytes. I'm willing to accept any kind of space optimisations to also fit in I/O initialisation in the 256 byte limit so it's self-contained in 256 bytes.