Building my first computer
I just came across the very first computer I ever built. Now I don’t mean plugging a CPU into a motherboard - to build this computer I had to solder in all the resistors, transistors, diodes, capacitors, LEDs, switches, chips etc.
The Microcomp-1 was a kit computer, produced by a small electronics magazine called Talking Electronics. This is a very simple computer based on the Z-80 CPU, with a stunning one whole byte of RAM and 16KB of EPROM storage. (The “one byte of RAM” is just an output latch to make driving the LEDs easier.) The input options consist of two micro-switches (labelled A and B on the board) and a “probe” (the orange fly-lead) which can be used as a simple logic-probe. (The probe is directly hooked up to the speaker.) The 8-way DIP switch is used to select the starting address in the EPROM.
Output options are two 7-segment LEDs, a 4×4 matrix of LEDs and 8 single LEDs. All three output options are on the same output bus, so they will all display the contents of the output bus, just in different ways. The rows of the 4×4 matrix is driven by the low 4-bits of the output latch while the columns are driven by the upper four bits. Using some simple multiplexing, it is possible to individually address each LED.
The clock speed is adjustable using a small trimpot (on the left hand edge of the board with an LED soldered to it to make it easier to turn) but I cannot for the life of me remember what speeds it was capable of.
This was a great little kit to build - I learned a lot about the design and operation of microcomputers using this. When I get some spare time I will dig out the manual and see if it still works…
July 24th, 2006 at 2:24 am
Nice, neat job! I never had the patience to be neat–I always wanted to see the thing work, so I rushed through it. Man, I should get into building boards again for fun; forgotten all the hardware stuff.
Shoot, I need my own little lab or something for this kinda stuff.
July 24th, 2006 at 12:22 pm
Well… You haven’t seen the solder side. ;^)
I started back on the electronics kick earlier this year, but my work room has been crowded out with too much junk. I really need to sort that shit out and get back to my work desk. I have a few unfinished projects that I want to get done…
August 17th, 2006 at 4:21 pm
What can this computer do?
August 17th, 2006 at 4:38 pm
Well, with the lack of memory (effectively just the Z80 registers), the lack of input (two buttons) and minimal output options, there’s not a great deal it can do. However it was a great way to learn about microcomputer design and operation.
The EPROM that came with the kit contained a handful of simple programs, ranging from scrolling text displays on the 7-seg LEDs, to reaction timers, to a two player “quick draw” game.
If I can find the manual I will post more details about how it worked and what it could do.
August 22nd, 2006 at 1:45 am
[...] I finally foung the magazine containing the details of the Micro-comp so I can now give you some more details. The magazine was a one-shot, called Six BD 679 Projects, and the first half contained details of six electronics construction projects based around the BD 679 Darlington power transistor, with the Micro-Comp taking up the remainder of the magazine. (I am at a loss to explain why the Micro-Comp wasn’t featured more prominently on the cover or in the title, but Talking Electronics is a weird mob…) The magazine was published in 1994 and reprinted articles and projects from the Talking Electronics magazine. Talking Electronics is a local electronics hobbyist company based in Melbourne. Back in the early 1980s (IIRC) TE launched an electronics magazine, which saw some moderate success despite its irregular publishing schedule. In all, fifteen issues of Talking Electronics were published and TE also published a number of one-shot magazines, including six Electronics Notebooks (similar to Forrest M Mims’ notebook series), a two-part Learning Electronics, Digital Electronics Revealed, numerous model railway and FM bug books and a few compilations of popular projects form the Talking electronics magazines. The magazines were generally pretty good and I learned a lot of my electronics chops by studying and building the projects presented therein. On to the Micro-Comp… [...]