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View Full Version : Timing-critical chips for replica Front Panel?



RickNel
October 20th, 2009, 07:56 PM
A friend and I are planning to build a couple of replica S-100 Front Panels based on the Ithaca Systems design. He's the engineer and considers that the timing specs on the DM96S02 one-shot chip are critical and can't be readily substituted without significant performance risk or redesign.

Any ideas on reliable sources for chips of this type? I've seen some large quantities with Chinese on-line suppliers, but would appreciate any experience anyone has had sourcing spec-critical chips like this. Should we beware of bad pulls or bum replica chips?

Also would appreciate any advice on practical and reliable work-arounds for one-shot circuits that would suit s-100, IEEE696-compliant Front Panel.

Has anyone else had success with building Front Panel from scratch sourcing components from current market?

Any advice would be appreciated.

thanks,

Rick

Chuck(G)
October 20th, 2009, 09:50 PM
Unicorn has the 96S02 (http://www.unicornelectronics.com) in stock. You can also use the AMD AM26S02 or even a 74S123, if you can find it (adjust pinout accordingly). That's just a seat-of-the-pants guess. Without seeing the circuit you're trying to use it in, it's hard to say for certain.

channelmaniac
October 21st, 2009, 06:33 AM
I'll check my stock... I had several tubes of the 9602 if I remember correctly...

Be careful of Chinese suppliers. You'll find a lot of counterfeit chips. :(

RJ

Chuck(G)
October 21st, 2009, 09:21 AM
I'll check my stock... I had several tubes of the 9602 if I remember correctly...

Be careful of Chinese suppliers. You'll find a lot of counterfeit chips. :(

The 96LS02 is still fairly easy to find, but the OP seems to want the 'S02 variant.

RickNel
October 21st, 2009, 03:52 PM
Thanks for the advice - will follow up.

@channelmaniac - re counterfeits, I was a bit suspicious seeing some chips listing manufacturer as Fairchild Semiconductor with manufacture date of 2008 and stock of >6000! Caveat emptor.

@chuck - yes, my instructions from my friend are that LS and other chip variants have small differences in propagation and response times that can cause problems in a circuit that is precisely tuned for the ieee696 spec 125ns clock half-cycle needed for 4MHz CPUs. Older Front Panels for 2MHz CPU were less demanding.

Ithaca Systems FP schematics are floating around on the net somewhere.

Chuck(G)
October 21st, 2009, 04:51 PM
Rick, I assume that the chip in question is IC 31. Half of it is used as a switch debounce, so that can't be the one.

So it must be the one that's used in the DEPOSIT circuitry. Yes, the S part has a low propogation delay.

Look for the NTE replacement: NTE96S02; it's offered by various places on the web. About 5 smackers.

channelmaniac
October 21st, 2009, 05:37 PM
I have 61 of them here... and glad I dug 'em out as I had a tube of PROMs, NOS Motorola 68766 EPROMs, some TMS5200 speech chips, and AY-3-8910 chips in the same bin. :D

NobodyIsHere
October 22nd, 2009, 03:30 AM
Hi! Are you planning on offering a PCB of the new frontpanel board?

Thanks and have a nice day!

Andrew Lynch

RickNel
October 22nd, 2009, 11:05 PM
Andrew - haven't yet thought beyond working out whether we can build the thing with currently-available parts. Proposing to build on your new proto-boards for a start!

I guess if we get a working prototype the next step could be to use KiCad or similar to do a proper PCB layout. Trailing quite a few stages behind you in that area!

But yes, if it works, perhaps a PCB could be another N8VEM project. In that case, though, it might be better to have more up-to-date design with more modern components. I'm aware of your ECB Bus Monitor that has quite a bit in common for the Z80 bus, though not all S-100 lines.

regards
Rick

NobodyIsHere
October 23rd, 2009, 04:11 AM
Hi! Please let me know what comes of your project. I think it would be a good PCB and there would be people interested in it.

If you are planning on using the new S-100 buffered prototyping boards please get with either John or me soonest as we are nearly ready to make a manufacturing order. Since the quantity is quite a bit lower than the last order of the regular (nonbuffered) S-100 prototyping boards the true unit price will be higher but still reasonable.

I would definitely like to make some more S-100 boards for the N8VEM project and am considering some ideas.

Thanks and have a nice day!

Andrew Lynch

Chuck(G)
October 24th, 2009, 08:32 PM
See my suggestion under "8088 pinouts" for running an analog voltmeter to measure instructions/seconds. You can use the Z80 M1 signal for that... :)

RickNel
October 25th, 2009, 04:37 AM
Hey Chuck - I didn't realise this forum hosted threads for interior decorators:winking:

Seriously though, I think there is plenty of scope (excuse the pun) to develop better visual diagnostic cues for the carers of ageing machines. My S-100 box is blessed with one simple power LED that tells me nothing at all about the machine beyond the power switch. Hence my interest in an external Front Panel and possibly export of full set of bus signals to the PC environment for more useful visual display.

But I like your "tachometer" idea. Swingenpoints as well as Blinkenlights!

Rick

Chuck(G)
October 25th, 2009, 10:00 AM
Hey, my old Integrand S100 box has a reset button on the front panel. That's it--not even a power switch (it's on the back of the system). Not even a "power" indicator. The folks at Integrand were into pure brute functionality (it's a great box, BTW, with a huge power supply and lots of slots).

A front panel would be pretty cool, but totally un-authentic on it.

A couple of the old GE mainframes had a "thousand operations per second" analog meter on the operator's console (the fact that it was a mainframe by GE tells you how long ago that was!).

Chuck(G)
October 25th, 2009, 04:46 PM
There were some very sexy front panels out there during the 60s and 70s. Honeywell had some of the best.

I recall seeing a magnificent operator's console on a water-cooled system at Honeywell's Phoenix plant sometime around 1975. This had not only blinkenlights and CRT displays, but Burroughs self-scan neon bar graph displays to show activity in various parts of the system. These big orange bars bouncing up and down as the machine did who-knew-what.

It's a shame, but other than the H200 and H316 and the H316 "kitchen computer", I can't find any images of Honeywell consoles on the web. The web barely turns up mention of Burroughs "Self Scan" displays.

billdeg
October 28th, 2009, 05:36 AM
If you have an "in circuit emulator" you can interface with the processor and the memory that way, kind of like a front panel. You can see where the bootstrap is loaded, if there are PROMs you can check the memory range for the Proms to verify the code is loaded, run memory card tests, etc.

I used one earlier this year to test an S-100 without I/O or a front panel to determine the operational status of the cards, etc.

Not sure who sells an "ICE" for your processor, or how expensive it'd be, but this will work.

Bill

RickNel
October 30th, 2009, 03:53 PM
Bill - there are plans and instructions for a Z80 ICE available here:

http://www.tauntek.com/Z80-In-Circuit-Emulator.htm

I'm involved in a project to build a replica Front Panel but am also mulling whether to put together a Z80 ICE like this one.

One of my system problems is a corrupted IPL ROM and no source code for it. So ability to intercept and debug the IPL is pretty challenging when I'm not sure what other hardware bugs might be causing trouble on any of 4 cards (I/O, CPU, RAM and FDC) that all have to be working for the IPL code to even load a working BIOS and CCP. I might need both tools plus lots of imagination.

Rick

billdeg
October 30th, 2009, 11:23 PM
Rick,
I have one of these, it works great and I recommend it if you can build one. I use it regularly for Z80 system diagnosis. I was able to get into a system when no other approach worked.

I was also involved in the testing of this device and I made some suggestions that were implemented in later versions. I did not design it however. I was just a tester.

Bill