Thursday, March 18, 2010

8085 Microprocessor Project: MAG-85

Here's a picture of the completed hand-wired circuit board for the MAG-85 (Micro Applications Gadget) 8085-based microcomputer system:
MAG-85, 8085 CPU computer with 8K RAM, 4x5 matrix keypad, LCD display,and 16 additional digital I/Os.

More info on this project at

I'm presently working on both a permanent front panel/enclosure and the permanent software. I'll be writing a machine language monitor program that will provide a number of utility routines for using the system's I/O.

The system has a 4x5 keypad,and an LCD display (16x2 is used here, I'll write the software to allow any two-line display from 16x2 to 40x2.) It also has 16 extra digital inputs and outputs. In the image eight of each are in use to read the state of a bank of DIP switches and display that on the 8 LEDs. The system can be expanded off-board with up to an additional 40 additional I/Os with the present I/O decoders.

The 8085's interrupt inputs are available as well, above I have switches on TRAP (the 8085's non-maskable interrupt) and RST7.5. RST6.5 is used by the keyboard, and RST5.5 will also be available on the front panel as a user program vector switch.

Everything's coming together nicely on this project now. I have detailed instructions on constructing the circuit on the project web page, with detailed instructions for a hand-wired board like the one above soon to come.