Trevor Makes' Breadboard EEPROM Burner Becomes a Full Z80 Microcomputer in a Serious Upgrade
A relatively simple EEPROM burner build has now feature-creeped its way to being a fully functional eight-bit microcomputer.
Computer engineer Trevor Makes is back with the breadboard creations, this time turning what started life off as a simple programmer for EEPROM chips into a fully-functional Zilog Z80-based microcomputer — with a little assistance from an Arduino Nano standing in for a monitor.
"I updated my last project, an EEPROM programmer, by adding a Z80 CPU and 32kB SRAM [Static RAM] to the computer bus," Makes explains of his now enlarged but still surprisingly neat breadboard project. "The Arduino has an assembler, disassembler, and memory commands built-in, so I can write Z80 code with any serial monitor."
Makes' creation started life as a burner for 28C-series parallel electrically erasable programmable read-only memory (EEPROM) chips, designed to work around the high cost of commercial devices capable of doing the same and the lack of parallel port for using period-appropriate hardware available at a lower cost. Built around an Arduino Nano, the burner used a pair of 74HC573 latches to provide a 64kB address space and burn Intel-format HEX files to chips in "a few seconds."
While that project was entirely functional as-was, Makes had a further idea: expanding the buld into a full computer by adding a Zilog Z80-compatible CPU plus 32kB of dedicated SRAM. The component count for the project is dramatically reduced by keeping the Arduino Nano in-place, this time to serve as a monitor for assembly-language programming.
To prove that device functional, Makes put together a simple program for ROT13 "encryption" — taking text input and cycling it 13 places up the alphabet to scramble it, or taking pre-scrambled ciphertext and pushing it another 13 places to return it to the original plain text. Makes has also pledged to launch a series of videos delving deeper into writing applications for the machine.
Makes' full video is now available on YouTube, while the source code and schematics are available on GitHub under the permissive MIT license.