40-pin CPU interface boss - is there anything like this?

[westveld]

I'm not sure what to call it - but I'm thinking of something that connects to the pins of a 40-pin CPU in-circuit.

Maybe uses an IC test clip to make the connection.

Maybe with an FPGA with 5v logic level converters.

In theory something like this could:

• Emulate ROM, IO, Disk, network, even display out
• Be a kind of logic sniffer right on the CPU
• Have firmware for each CPU type - 8088, 6502, Z80, etc.

I've seen stuff that replaces / emulates the CPU, like:
https://hackaday.io/project/165624-mocka65xx-universal-650285xx-cpu-replacement

Does this exist (yet) ?

Thoughts?

 

[Chuck(G)]

Do you mean something like the attachment used by many ICEs?

No, never heard of anything like that.... /s

 

[westveld]

Yeah, a more flexible, open source version of that.

Thanks - that should start me on a new thread to follow!

 

[Chuck(G)]

Maybe you should look into test clips

 

[Hugo Holden]

Maybe you should look into test clips

That talk of test clips reminded me that some 20 years ago. I think I posted this story many years ago.

I wanted one of the common test probes that was around in the 1970's, it would clip onto a 74 series logic IC and show its logic levels. Obviously it couldn't see low duty cycle pulses but it was a very handy tool, especially for crtain TTL logic circuits where the voltages are largely stable. The thing is it was powered by the IC power automatically. The pin with the highest average voltage lit the LED brighter and the power supply pin lit that LED brighter than all the rest.

When I went to buy one the only remaining supplier I could easily get one from, they were insanely expensive. So I decided to design my own using Logic IC test clips and adding two small hand wired spot stlye proto pcbs over the contacts with some surface mount resistors, surface mount LED's and some 1N4148 diodes, so they still can be used a "test clip"

The diode array creates a virtual power supply by provide the pathway for ground and +5V (whatever pin they are on). I have attached the schematic, old and hand drawn with some of the original calculations.

 

[Chuck(G)]

I posted the link to the 3M brochure as most of these test clips used to be manufactured by AP. K and H apparently still make them (or rebadge the 3M ones). Pomona also has them, but they're definitely inferior to the AP/3M ones.

 

[MattisLind]

Perhaps you are looking for something like this: https://github.com/hoglet67/AtomBusMon

 

[westveld]

Perhaps you are looking for something like this: https://github.com/hoglet67/AtomBusMon

I did see that - I thought it was kaput since the GODIL was unavailable, but it looks like they have other options now.

I was thinking something at a simpler level, not emulating the CPU, just accessing the bus via the CPU directly.

So instead of using the ROM socket to try an alternate ROM (for example), attach right to the bus at the CPU.

I have a bunch of machines at the moment with different ROM configurations, different 40 pin CPUs.

Most with some sort of issue to sort out.

I do need to read up on the AtomBusMon - looks like there are lots of good ideas there!

 

[MattisLind]

At this point almost everything spelled semiconductor is unobtainium. Hope fully it will solve not too far in the future. As far as I understand Dave have adapted to a XC6SLX9 board from ebay seller eepizza. But I would guess that any board with the same chip can be made to work.

I have another similar looking XC6SLX9 board which I have vague plans to use AtomBusMonitor on. The idea would then be to adapt it to the 68008 processor so I could fix one of my ABC1600 which has an odd fault. Lets see if I manage to understand the VHDL so that I can add a 68000 core on it.

 

[Plasma]

I did see that - I thought it was kaput since the GODIL was unavailable, but it looks like they have other options now.

I was thinking something at a simpler level, not emulating the CPU, just accessing the bus via the CPU directly.

So instead of using the ROM socket to try an alternate ROM (for example), attach right to the bus at the CPU.

I have a bunch of machines at the moment with different ROM configurations, different 40 pin CPUs.

Most with some sort of issue to sort out.

I do need to read up on the AtomBusMon - looks like there are lots of good ideas there!

There are several EPROM emulators out there if that's all you need. I have the Moates Ostrich 2 and it works well. It's intended for tuning automotive ECMs, but with EmUtility you can use it for anything.

Here is a homebrew one that's less polished but cheaper.

 

[westveld]

There are several EPROM emulators out there if that's all you need. I have the Moates Ostrich 2 and it works well. It's intended for tuning automotive ECMs, but with EmUtility you can use it for anything.

Here is a homebrew one that's less polished but cheaper.

I just got one of the those EPROM-EMU-NG units recently - pretty cool, makes testing things easy and quick.