8008 and Z80 ICEs

[JonB]

Hi all

I've just completed re-engineering Bob Grieb's Tauntek 8080-ICE as he doesn't make them any more:





I've got permission to offer these, so is there any interest in this board or the Z80-ICE (which I plan to do next)?

Cheers
JonB

 

[lowen]

Yes on the Z80 board. Nice work, by the way.

 

[gekaufman]

Jon -

Nice work! I arranged a run of the original boards a while back. Unfortunately sourcing the original CPLD was difficult.

https://www.retrobrewcomputers.org/doku.php?id=builderpages:gary_kaufman:z80ice

I've had occasional requests from folks about availability, so I'm sure there will be interest.

- Gary

 

[BloodyCactus]

Are not the XC9536's hard to get now they have been OOP for quite a few years? Do you plan on redesigning it to remove the obsolete parts?

 

[JonB]

It was redesigned to take the 3.3v variant - 9536XL. There's a jumper onboard to set the CPLD voltage. The one pictured uses the PC44 package (socketed). It works with the 5v and 3.3v part. This means you can use whatever is available. The only fly in the ointment is that there are glitches with the MD and MT commands. I'm looking into it. Otherwise, it works fine.

To redesign for a newer CPLD would take a lot longer, because I'd have to learn more about CPLDs. But that doesn't seem necessary because I can still order the 3.3v CPLD in an SMT package from Farnell. So a board that can use these chips is do-able, at least for the time being.

 

[ldkraemer]

JonB,
I'm interested in the Z80ICE (one or possibly 2).

Larry

 

[glitch]

I'd be interested in one of each. Thanks for reviving this project!

I was over-excited to see "8008" in the title -- perhaps a moderator can correct that?

 

[Dwight Elvey]

I've often thought about creating a CPU substitute for these older machine. For the most part, we rarely do development of Z80 and 8080 machines, we are mostly diagnosing and repairing these machines. For diagnosing, we rarely need to run the original code on the machine. In fact, the original code is a poor diagnostic tool. It rarely repeats a sequence but once on reset that we need to analyse. Any need for an ICE to develop a machine can usually be done with a ROM ICE ( a much simpler setup ). We have cheap controllers that run at 72Mhz or greater that can run I/O fast enough to run diagnostics on a 8080 or Z80 bus. The interface would be mostly buffers. No additional programmable devices are needed.
Dwight

 

[Al Kossow]

We have cheap controllers that run at 72Mhz or greater that can run I/O fast enough to run diagnostics on a 8080 or Z80 bus. The interface would be mostly buffers. No additional programmable devices are needed.
Dwight

That's nice.
Why re-invent the wheel?
This is a solved problem.

 

[BloodyCactus]

Im curious how well the 3.3v CPLD drives 5v TTL CPU lines and downstream TTL logic.

 

[JonB]

@BloodyCactus: It just works.. The official level of a TTL "High" signal (according to Wikipedia) is from 2.0v - Vcc (5v), so a 3.3v high level would count as a 1 when read by a TTL IC. The CPLD only has to drive the first input signal of a TTL device; all ongoing signals would be at 5v. What is more important is the signals coming into the CPLD. If its (input) pins are not 5v tolerant there will be damage, but the part I am using (XC9536XL) is 5v tolerant.

 

[8008guy]

I'd be interested in one of each. Thanks for reviving this project!

I was over-excited to see "8008" in the title -- perhaps a moderator can correct that?

Yep, ditto on that

 

[Randy McLaughlin]

Do you have any ice boards fore sale, and if so how much are they?

Thank you,


Randy

 

[Svenska]

Im curious how well the 3.3v CPLD drives 5v TTL CPU lines and downstream TTL logic.

Also keep in mind that old NMOS TTL only outputs ~3V anyway. Confused me quite a lot when doing my Z80 board.

 

[lowen]

Also keep in mind that old NMOS TTL only outputs ~3V anyway. Confused me quite a lot when doing my Z80 board.

Indeed. TTL "outputs" don't actually output voltage directly.... they sink current that is sourced by the "inputs." NMOS wa designed to be somewhat compatible with TTL, but MOS inputs are not current sources, and that can complicate things sometimes. I still remember the first few weeks of the first semester of digital systems in college; long ago enough that we still breadboarded 7400-series TTL directly, rather than using one of the many University Program boards from Altera and others to do digital logic in FPGAs. Everyone in the class was pretty confused about what the professor was saying about inputs being the current sources and outputs being sinks, and how TTL outputs have so much more drive capability outputting a low than a high. It was actually several weeks into the semester before the analog bipolar transistor theory class caught up with the digital systems class, and then all of a sudden it clicked why TTL inputs and outputs are the way they are...... and why fan-out and fan-in are 'things' and need to be paid attention to.

The analysis of the logic high output is a little different from the logic low output, but it still goes to a collector-emitter drop plus a diode drop, but that diode drop is current-dependent.... been a long time since I did the analog analysis of the totem-pole output and how it 'fast floats' the input.