I love logic analyzers. They make it so easy to see what’s going on in a digital system. Sometimes, a logic analyzer is the only tool that can catch an issue in your design, or the only way to help fix a broken board.
While they’re not as useful as they once were, given the shift towards serial communication and the fact that most scopes now come with serial decoders, they are awesome for fixing 20-30 year old hardware…. and the best part is, they can be acquired for cheap!
But… there is one thing that just plain sucks… and that’s hooking one up to the circuit. I mean, on a typical old design, you’ll have at least a 16bit address bus and 8 bits of data, plus several control lines, so that’s at least 25-30 probes to hook up. Try doing that fast without making any mistakes.
It almost makes it not worth it… unless you use one of my awesome logic analyzer adapters. I built these because I just simply can’t be bothered hooking these up, since most of the checks that I do don’t require the logic analyzer to be hooked up to the circuit for more than a few minutes.
I normally need to check how the CPU accesses the bus, is it reading the right data from the right addresses when it’s staring up, is there anything stuck on the bus, are any control lines not functioning as I expect them to, and are these signals getting to the rest of the bus.
For this type of activity I designed these to make this process quick. The idea here is to plug the adapter into a CPU, RAM or ROM socket, load up the config file, plug the analyzer PODs into the adapter, and then do a scan.
With these the process only takes a few minutes. I don’t have to worry about all the probes, where all the data / address / control lines are, and whether I’m going to make mistakes hooking everything up. I’m providing the config files for the logic analyzer as well so you just load them and go.
Of course I’m building these for the analyzer that I have, which is the HP / Agilent model with the 40 pin PODs. These adapters also have the termination network built in, so they’re plug and play.
So far I have produced the following adapters:
- 8086 / 8088 CPU
- 8051 MPU
- Z80 CPU
- 6502 / 6800 CPU
- 6801 / 6803 / HD6303 CPUs
- 27XXX series ROMs
Planning to make an adapter for most popular CPUs, MCUs, RAM and ROM ics.
This project is still work in progress. There is a little more to be done before I release these to the public. If there is a lot of interest I will end up making these for other logic analyzers as well.
Stay tuned for more info…