The Scelbi MEA (Monitor Editor Assembler) was the official ROM-resident software for the Scelbi-8B and Scelbi-8H microcomputers. It resided in 4K of 1702 EPROM from octal address 0600 000 to 077 377 and turned the bare 8008 hardware into a usable development system by providing a complete monitor, line editor, and assembler. In the MicroBasement, MEA represents the very first practical software environment for hobbyist 8008 machines — the tool that let builders write, edit, assemble, and run real programs directly from the front panel or a serial terminal. This write-up covers MEA’s history, functionality, commands, and a real-world demo of starting it on a physical Scelbi using Tera Term.
MEA was written in 1974–1975 by the Scelbi Computer Consulting team (primarily Nat Wadsworth and his engineers) specifically for the Scelbi-8B. It occupied 4K of 1702 EPROM from octal address 0600 000 to 077 377 and was supplied on pre-programmed EPROMs with every Scelbi-8B kit. MEA was revolutionary because it gave users a full development environment without needing a separate computer or expensive paper-tape system. It was one of the earliest examples of a complete “monitor + editor + assembler” in a single ROM set for a personal microcomputer.
MEA combined three major tools in one 4K ROM package:
It supported 110 baud serial communication (perfect for early terminals or Tera Term) and worked beautifully with the Scelbi’s front panel for debugging.
Here is the exact step-by-step procedure to launch MEA on a physical Scelbi-8B or compatible system:
| Starting MEA on a Real Scelbi | |
|---|---|
| Step | Action |
| 1 | Start Tera Term on your modern computer |
| 2 | Select Serial Port and configure: 110 Baud, 7 data bits, Parity = None (0), 1 stop bit |
| 3 | On the Scelbi front panel, set the address/data switches to JMP 000 060 |
| 4 | Set Switches to Data 104 (octal for JMP) |
| 5 | Press INT (or RESET if needed) |
| 6 | Press STEP |
| 7 | Set Switches to 000 |
| 8 | Press STEP |
| 9 | Set Switches to 060 |
| 10 | Press STEP |
| 11 | Press RUN |
| 12 | You should now see the MEA prompt (*) on Tera Term |
Once at the MEA prompt (*), you can dump a range of memory with the F (Fill/Dump) command:
F 060 000,070 000 <enter>
This displays memory from address 060 000 to 070 000 octal in a clean formatted listing.
MEA was the first complete development environment most hobbyists ever had on a personal computer. It proved that a tiny 8008 system could be a real programming platform. In the MicroBasement, it stands as a proud piece of early microcomputer history — the software that turned the Mark 8 and Scelbi machines from blinking lights into usable computers. Many of today’s embedded developers trace their roots back to typing commands into a 1975 Scelbi running MEA.