Small Computer Monitor

The Small Computer Monitor is a classic machine code monitor for Z80 based systems.

SCM screen shot

It has the following main features:

  • Boot loader to load Intel HEX files from a PC or similar
  • Memory display and editing
  • Register display and editing
  • In-line disassembler
  • In-line assembler
  • Breakpoint debugging
  • Single step debugging (without the need for special hardware)
  • Extendable using its built in ROM filing system

Systems limited to 8k byte ROMs are supported, but there is no space for extensions using the Monitor’s ROM filing system. Systems with larger ROMs have versions of the Monitor that include BASIC and a CP/M loader.

The ROM filing system allows additional files to be included in the ROM. These can be programs or help text. These files are automatically integrated into the Monitor, providing an easy way to extend its functionality.

Currently, the Small Computer Monitor supports the following systems:

Latest release (v1.0.0) complete with source code, tutorial, user guide and development environment:

SCWorkshop v0.2.0 plus SCMonitor v1.0.0.20190124 (ZIP)

Pre-built ROM images (HEX files) can be found in the folder:


Related documentation

Small Computer Monitor Installation edition 1.0.0 (PDF)

Small Computer Monitor Tutorial edition 1.0.0 (PDF)

Small Computer Monitor User Guide edition 1.0.0 (PDF)

Small Computer Monitor Reference Sheet edition 1.0.0 (PDF) Online Assembler Tutorial edition 1.0.0 (PDF)

SCMonitor was originally entirely my own work starting completely from scratch. However, since the first release of SCMonitor I’ve had lots of feedback and input from others. I would particularly like to thank Jon Langseth, designer of the LiNC80 SBC1, for all his input and enthusiasm during the work on the LiNC80 version and the general v1.0 release.

Third party support

Francis Piérot’s cross-platform assembler enables the Small Computer Monitor to be assembled on Mac OS, Linux, and Windows.

MUZ-Assembler by Francis Piérot

MUZ-Assembler documentation by Francis Piérot

Bill Shen has ported the Small Computer Monitor to a number of designs, including:

Z280RC, a CP/M ready SBC based on Z280 CPU

Z80SBC64, a hobbyist-friendly Z80 SBC

2 thoughts on “Small Computer Monitor”

  1. Hi Stephen

    Are you able to describe the Small Computer Monitor ROM build process for a LiNC80 system (32K ROM)? What needs to be changed in the !Main.asm source file? Which source files need to be compiled? How should all of the .hex files in the Output folder be joined together, and in what order? It would be good to have some clear and precise instructions to follow.


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