Microprocessor Bus Testers

[ortek_service]

A new thread to discuss these types of service-aids test equipment units - After some initial discussions had taken place on the 'Unhappy AIM-65' thread (posts #30-#35), at: https://www.vintage-radio.net/forum/...46#post1555646

And I'm copying posts #30 to #35 from that thread, myself, to posts below - For context reference (as my requests to do this to mods via report function a couple of times + posting this request in that thread hadn't worked)

[ortek_service]

From https://www.vintage-radio.net/forum/...5&postcount=30

Originally Posted by ortek_service

Co-incidentally, I also picked-up one of these Polar Instruments B2000A uP BUS Tester with printer for a few pounds nearly 30 yrs ago. But I never used it, as it was missing any probes, and I think that was before eBay / the Internet was common. So I'll have to look into getting some for it.
I did also pick-up a Dataman MicroDoc a while later, that looks like it has similar capabilities and luckily did come with a few common CPU plug-in probe adaptor boards. But I'm still trying to recall where that went, to look at documenting what's in it, as there doesn't really seem to be any info on it on the 'net.

[ortek_service]

From: https://www.vintage-radio.net/forum/...6&postcount=31

Originally Posted by Pamphonica

If you drop me a PM with your email address I will send you all the details I have on the B2000/A. I should also be able to provide some personality modules and photos of the cables.

-Jeremy

[ortek_service]

From: https://www.vintage-radio.net/forum/...5&postcount=32

Originally Posted by ortek_service

Thanks - PM now sent.

I've just found my Polar B2000A (Not sure yet what the A-suffix version gave you extra), which I'd got at Telford 1999 Radio Rally for £1 (without any pods) and opened it up (possibly for first time), discovering a Z80 (ironic you've used it to repair a 6502 system !) + SRM2016 SRAM, 27128 EPROM (readout and attached my B2000A's version marked NP27 with 8543- date-code?), and 8255 PIA + loads of 74HC/LS373's.
I also found an infamous 3.6V 100mAh PCB-mounted NiCad - with the usual legs on some adjacent parts starting to go green. So will whip that out and maybe replace with an off-board 3xAAA holder and NiMH Low Self-Discharge cells for better memory retention if that's important.

A quick Google also found it discussed on Arcade-machine repair forums / a copy of the manual - as well as your recent post of EEVBlog about replacement pods: https://www.eevblog.com/forum/testge...up-bus-tester/

Surprisingly, Polar Instruments (Most well known for their famous 'Toneohm' PCB short-locator repair aid, I've also got some of - and first I got was also missing its Kelvin-connection wired? probes) are still around.
But they now mostly do PCB-design aids software products, and only test equipment still listed as current is an updated Toneohm + a rather-more expensive / professional-use Flying probe tester. It seems the B2000A was rather short-lived, by 1987 being discontinued (their first product to be): https://www.polarinstruments.com/sup..._warranty.html

I did also find I had a rather more obscure CIL Microsystems Ltd PCI-1281 16 channel Logic Analyser ? in the same-size case. This was also had a Z80(A), along with four! Z80A-PIO's and a Z80A-SIO for its RS232 Interface. I can't seem to find much info on this on the'net, and wonder if those v.cheap USB LogiC Analysers from China are more powerful these days.
But I've also readout the CIL PCI-1281's 2732 4K EPROM - finding Z80 Mnemonics in this! (So looks like it may have produced Disassembly output).

See attached zip of the readout-firmware for both of these, for interest / archiving for possible future repairs.
With the Dataman Microdoctor also long-discontinued. maybe there might be some interest in re-creating (an open-source, for maintainability, unlike some Arcade-machine IC testers) one, possibly using an Arduino (Mega?) / RPi controller, to assist in repairing 6502 / z80 etc. 8bit systems that won't boot-up and maybe easier to diagnose via the processor's bus to check memory map etc.

[ortek_service]

From: https://www.vintage-radio.net/forum/...1&postcount=33

Originally Posted by TonyDuell

Firstly a word of warning about 'whipping out the NiCd'. I've met many devices that charge said backup battery through a resistor from a 12V or so rail. They use the battery effectively as a shunt regualtor to keep the backup voltage at around 3.6V. This is then fed via a diode to the RAM +5V line (with another diode to supply the RAM from the normal 5V line when the thing is powered up). The result is that if the battery goes open-circuit or is removed the RAM is effectively powered from 12V which it tends not to like.

Do check the circuit and if necessary disable the charger or stick a 3V9 zener diode across the battery connections in place of the battery.

Anyway...

I have a strange logic analyser made by Zircon Insturments. It's quite slow, but has a lot of channels and I suspect was designed for educational use. The pod I have for it has 4 off 40 pin headers on it so that a straight-through ribbon cable ending in one of those DIP-Clips can be put onto a Z80, 6502, 6800 or 6809 processor and it will route the address and data pins, etc, to sensible inputs of the analyser.

As I mentioned in the Osborne restoration message, I have a full in-circuit emulator for the Z80 (only). Although it will run Z80 code, let you set breakpoints, etc, most of the time I just use it as a bus tester to access RAM memory and I/O ports in whatever I am repairing. So a more general bus tester would be of interest. I would prefer it if it was a stand-alone device with its own keypad/display or perhaps a connection for a serial terminal rather than something to hang off a USB port. There isn't room for a PC on my bench. The processors I would want to be able to handle are the Z80, 6502, 6809 and 8085.

[ortek_service]

From: https://www.vintage-radio.net/forum/...7&postcount=34

Originally Posted by ortek_service

Yes, I was intending on replacing the obsolete NiCad with a same-voltage equivalent. But have read elsewhere on here that the replacement NiMH PCB-Mounted batteries can also leak a bit and that mounting one off-board may be safer to prevent any more corrosion of the PCB and nearby components.

So I'd like to remove original NiCad fairly-soon, to prevent more damage occurring - Thanks for info about some equipment charging it from a 12V rail / using it as a regulator, which seems a rather dodgy thing to do.. I've only ever seen these being charged from the main +5V rail.

I've checked the circuit in the back of the manual, and confirmed the Polar B2000 does also do this (and has a 200R resistor in series with battery, so wouldn't shunt that much). They have actually also included a C106D thyristor over-voltage crowbar on the PSU main output - Although that's a bit over 5V, as there's a diode-drop feeding the +5Vcc rail - rather than having the crowbar directly across +5Vcc (Not sure if this could be lifted by mis-connection of the pods to a higher voltage on target system etc, which could be wise to guard against).

The Polar B2000 supported the usual Z80, 8085, 6502 & 6800 (but might be able to extend that to a 6809). I do vaguely recall the Zircon make - There were quite a few companies back then (Inc. Philips-Fluke) who made this type of thing, but these now seem to have all gone, so probably some requirement for a suitable replacement being available.

[ortek_service]

From: https://www.vintage-radio.net/forum/...7&postcount=35

Originally Posted by Pamphonica

Now if only we could get someone to make up a replica PCB! I reckon its a fine little device. The only odd component (apart from a till-roll printer) is the 14-segment 8-digit LCD display. It seems to be fed by a 4-bit data bus and a strobe, plus 5V and ground. I tried to find an alternative (in case mine collapses) but no luck so far. Does the B2000A use the same display? Maybe we could get some photos (inside and out).
Another happy coincidence is that the AIM65 and the B2000 bus tester both use the same width thermal paper. Perfect!
We may need to split this thread. It's turned into a bus-tester fanzine!

[ortek_service]

Originally Posted by ortek_service

Thanks - PM now sent.

I've just found my Polar B2000A (Not sure yet what the A-suffix version gave you extra), which I'd got at Telford 1999 Radio Rally for £1 (without any pods) and opened it up (possibly for first time), discovering a Z80 (ironic you've used it to repair a 6502 system !) + SRM2016 SRAM, 27128 EPROM (readout and attached my B2000A's version marked NP27 with 8543- date-code?), and 8255 PIA + loads of 74HC/LS373's.
I also found an infamous 3.6V 100mAh PCB-mounted NiCad - with the usual legs on some adjacent parts starting to go green. So will whip that out and maybe replace with an off-board 3xAAA holder and NiMH Low Self-Discharge cells for better memory retention if that's important.

A quick Google also found it discussed on Arcade-machine repair forums / a copy of the manual - as well as your recent post of EEVBlog about replacement pods: https://www.eevblog.com/forum/testge...up-bus-tester/

Surprisingly, Polar Instruments (Most well known for their famous 'Toneohm' PCB short-locator repair aid, I've also got some of - and first I got was also missing its Kelvin-connection wired? probes) are still around.
But they now mostly do PCB-design aids software products, and only test equipment still listed as current is an updated Toneohm + a rather-more expensive / professional-use Flying probe tester. It seems the B2000A was rather short-lived, by 1987 being discontinued (their first product to be): https://www.polarinstruments.com/sup..._warranty.html

I've now finally edited my photos of my Polar Electronics Ltd B2000A - Inside & Outside, to get them down to a reasonable size to attach here (Plus titled i,ages fiilenames, to describe what they show), attaching all of these for reference here (+ re-attached previously attached copy of its 'NP27' version firmware readout, as a separate single EPROM-image .zip)


Some links to other Polar Electronics Ltd (Now Polar Instruments) B2000(A) Info:

Current Polar Instruments website, with date of last-manufacture of these products: https://www.polarinstruments.com/sup..._warranty.html


German Polar Instruments website, with links to manuals for some of their old products - but most links now unfortunately broken (like B2000/B200A Service Manual in English) / manuals links that do still work are mainly German ones: https://www.polarinstruments.com/de/...s/manuals.html

Their B3T model (+ pods) - Last made in 1994 - looks like it may have superseded the B2000/ B2000A (+ pods) - Last made in 1987.
And German User Manual is available from above weblink


The only manual to be found for the (original only) B2000 model, seems to be the User Manual, rather than Service Manual. And mainly found on Arcade machine info websites, such as: http://gamearchive.askey.org/General...olarB2000.pdf.


Discussions pamphonica (Jeremy) on here had instigated about the B2000 recently, and provided photos / connection details on B2000 + personality modules / B2000A external pod case: https://www.eevblog.com/forum/testge...up-bus-tester/

[ortek_service]

Originally Posted by ortek_service

>>
>>
I did also find I had a rather more obscure CIL Microsystems Ltd PCI-1281 16 channel Logic Analyser ? in the same-size case. This was also had a Z80(A), along with four! Z80A-PIO's and a Z80A-SIO for its RS232 Interface. I can't seem to find much info on this on the'net, and wonder if those v.cheap USB LogiC Analysers from China are more powerful these days.
But I've also readout the CIL PCI-1281's 2732 4K EPROM - finding Z80 Mnemonics in this! (So looks like it may have produced Disassembly output).
>>
>>

I've now also finally edited my photos of my CIL Microsystems Ltd PCI-1281 16 channel Logic Analyser ? Inside & Outside, to get them down to a reasonable size to attach here (Plus titled i,ages fiilenames, to describe what they show), attaching all of these for reference here (+ re-attached previously attached copy of its firmware readout, as a separate single EPROM-image .zip)

I've not been able to really find anything about this unit / much else about CIL Microsystems on the 'net.
And Surprisingly, it seems they never originally put a label over the UV-EPROM's window (but hopefully contents have all survived OK!), so I've now added one to it to try and protect it better in future.

I need to do some repair-work an internal ribbon-cable, which has previously got trapped by case-halves screws and cut-through some wires at the end!

[ortek_service]

Originally Posted by ortek_service

>>
>>
I did also find I had a rather more obscure CIL Microsystems Ltd PCI-1281 16 channel Logic Analyser ? in the same-size case. This was also had a Z80(A), along with four! Z80A-PIO's and a Z80A-SIO for its RS232 Interface. I can't seem to find much info on this on the'net, and wonder if those v.cheap USB LogiC Analysers from China are more powerful these days.
But I've also readout the CIL PCI-1281's 2732 4K EPROM - finding Z80 Mnemonics in this! (So looks like it may have produced Disassembly output).
>>
>>

This was another (equally-obscure) CIL-Microsystems PCI-2080 unit I also got from an old work's disposal sell-off. Whilst not really being a bus-tester - being a GPIB-Controlled Relay-switch, I thought was of interest to see how much of the Z80 chipset design they re-used from the PCI-1281.

I noticed they also didn't bother covering the UV-EPROM's window on this one, either!.
And they also seem to have forgot (unless someone has got at it) to bolt a regulator down, but there's still a mica washer under it, above the large heatsink! So I can't see it working for very long.
(Strange also that the heatsink goes under the transformer, to cook that a bit unnecessarily).

I have twisted the very-long separate mains wires together, to try and prevent them contacting low-voltage parts / getting cut into by case screws! - I'm not sure it would be too compliant with more-recent safety-standards...

[SiriusHardware]

Although not in the same league as any of these 'proper' testers, some of the simpler systems lend themselves to being fault-found by wiring something like an Arduino Mega into the CPU socket.

This is only really easy to do if the system only uses static (Not dynamic) RAM and there are no elements of the circuit which require the CPU to run at full speed to work, such as a video output - so something like an MK14 or other microprocessor trainer would be a good target for this type of approach.

Trying the same thing on a more complex system would carry with it an understanding that most of the system would not work while you were 'exercising' whatever part of the circuit it is you were interested in testing, but it is a valid way of testing various parts of a micro system as long as you understand the limitations. With some ingenuity it should be possible to generate / emulate some of the signals which the original CPU would generate, such as the clock-out on a 6502 or the Address Latch Enable (ALE) on micros with multiplexed address / data buses.

[ortek_service]

Well, as these original 'Bus Tester' units all now seem to have been long since discontinued, with no replacements / rarely seem to appear on surplus market, then I thought it would be quite-useful to recreate a more-modern fairly low-cost and open-source community supported version (hence this thread).
- And this could well be based on an Arduino (Mega ?) etc. as the original ones only have a Z80 and a small amount of memory, with the Interface circuitry on a shield. Using an existing uC modules, would save a bit of complexity of the design / PCB. Plus probably ditch the till-roll printer and have a multi-line LCD, with scroll etc / an asynchronous-serial output to a PC terminal program etc.

So if we can build a collection of the firmware of the various ones of these, then can disassemble the code to provide a basis of what to include in the (C etc? source for a more generic / portable across uC's) source code.


But the main other thing we're lacking is the schematics for any of these.
- Especially as the Service Manual (That was also English version), on a Polar Instruments German website webpage, is now a dead link
http://www.polarinstruments.com/manu...e%20manual.pdf

However, they don't really appear to be that complex - essentially a small uP-based computer system with quite a bit of digital I/O and some bus-buffers.
- And the Polar B2000 'Personality Modules' / B2000A Pods containing these, are just passive pin-mappers
So shouldn't be too difficult to fully rev-eng these, given a bit of time to trace all the (only 2 layer PCB)b tracks.


Also, looking at some of the original Polar B2000 'Personaity Modules', they looked extremely-similar to the ones used on the Dataman Microdoc(tor)
- except on that, they plugged into the top, rather than having to take lid off to change / have each enclosed in external pods on the B2000A.

So I'm thinking these could be quite similar (both have a built-in till-roll printer, for results of tests) - Just wish I could find mine, to open-up & document, being as any info on these is somewhat lacking on the 'net.

There is some circuitry of Pods in the later Polar B3T User-manual, that is accessible here: http://www.polarinstruments.com/manu...schematics.pdf

[Trigon.]

Is this any help?

PolarB2000.pdf

Cheers

[ortek_service]

Thanks - Yes it seems I'd forgotten this User-manual does actually have the schematics for the original B2000 version. And also a partial disassemblu of the firmware, with the I/O routines and comments.

And ironically, I'd actually previously linked to the exact same version of this:

Originally Posted by ortek_service

>>
>>
The only manual to be found for the (original only) B2000 model, seems to be the User Manual, rather than Service Manual. And mainly found on Arcade machine info websites, such as: http://gamearchive.askey.org/General...olarB2000.pdf.
>>
>>

- But I then later forgot that the schematics were in there for the B2000 model it covered:

Originally Posted by ortek_service

>>
>>
But the main other thing we're lacking is the schematics for any of these.
- Especially as the Service Manual (That was also English version), on a Polar Instruments German website webpage, is now a dead link
http://www.polarinstruments.com/manu...e%20manual.pdf
>>
>>

Although it would still be nice to find a copy of the service manual (as the broken link from that German Polar website, said it also covered the later B2000A version, and may also have some additional useful info on the design).


I've also found that the 27128 EPROM fitted in my B2000A, is twice the size of the B2000's schematic 2764 EPROM. And although the 27128's lower and upper 8KB 'halves' are quite similar, they are not exactly the same with the upper-8KB also having more non-FF 'data' at the end.
So I'm wondering if it might have a B2000 and a B2000A version in it, selected by the A13 address line and this is set differently between the two versions.

[TelecomTrev]

Hi, I've got a Z80 pod for a B2000A. I saved it from the bin in a workplace closure, someone else had already taken the B2000A some time before. I think it came with the unit but was never used - wrong CPU for what we did.
I've been holding onto it since the 1980s hoping to bump into another B2000A, as I found it a nice way to check the basics on microsystems without the then costs of logic analysers. I can post pics and info if anyone would like to see the insides.

Trev.

[ortek_service]

Hello Trev,

Thanks for the post, and welcome to this forum - You'll find your first few posts will require moderator approval, so may take a while to appear.

I had a similar, although opposite, situation that I picked-up the B2000A but didn't have any pods. But thanks to discovering information recently posted by Jeremy ('Pamphonica') on here / eevblog and the universal patch-PCB he's created ad kindly supplied me one for the original B2000 (/ fitting inside a B2000A pod?) plus links to the original B2000 manual that has wiring for the original pods, then I should now be able to finally get mine running.

It should be possible to create a rebuild/replica of the B2000 main unit (although the printer / display if not standard types, may be a bit more difficult), as they do provide the circuit for it in the user manual.
However, might need to get a copy of the original 8KB 2764 EPROM firmware for that one (Maybe Jeremy might be able to readout his, to have a backup, if not done already?).

The B2000A I have, which I haven't found a circuit for yet (but looks to be very-similar to the original B2000) uses a 16KB 27128 EPROM for its later firmware which I posted a copy of here. However, looking through the binary image file for that, in a Hex-editor, it looks like it may actually contain two versions in the two upper & lower 8KB halves, as the version display text appears twice at the same point in both upper and lower 8KB halves. But one of these halves is longer / they have different hex-code between them, so I'm wondering if only half of this 16KB EPROM is actually used, with upper A13 address line tied high or low on the B2000A (A13 on the 27128 is n.c. on the original 2764 and appears to be left unconnected on the original B2000 circuit).

It's probably also possible to create a more-modern Arduino (Mega?) etc. based equivalent for this, that could be supported by the open-source community. But it would require porting the original Z80 code, after disassembling this (there is a partial listing of I/O routines in the manual) and commenting it / understanding exactly what it all does. This could retain the same connector pinouts, for compatibility with legacy Polar pods / maybe add some more (my B2000A does have more listed on the rear, than were in the original B2000's manual, but some of these are hand-written / engraved into the blank boxes after the originally printed main types).

It would be nice, Trev, to see some pictures of your B2000A Z80 pod - both outside and inside (preferably both sides of the PCB). So please post these on here, if you are able to - The only 'B2000A external pod' I've seen is one that Jeremy got with his B2000, shown here:
https://www.eevblog.com/forum/testge...up-bus-tester/
And it seems this was originally a special (rather hand-crafted? from all those patch wires) one that was used to modify the 8085? (Although unit was labelled Z80?) personality module's connections to suit an 8031
However, that seemed a strange thing for Polar to do, when it would have maybe been cheaper for them to just make another 8031 personality module for the B2000 (as this 8031 external pod wouldn't work on the B2000A, if wiring had already been re-mapped by the 8085 personality-module and not B2000A straight-though wired to the external pod connector).

[TelecomTrev]

Ok, here's my first go at posting some pics. As previously mentioned these are of the insides of the Z80 pod for the B2000A.
The 40 pin DIL header to plug into the target system is on the left in the images.

[SiriusHardware]

I wonder how much that 'box with a 74LS74 chip in it' originally cost? I shudder to imagine. Looks like that ought to be really easy to reverse - engineer if you were able to take a look at the other side of the PCB as well.

[ortek_service]

Originally Posted by TelecomTrev

Ok, here's my first go at posting some pics. As previously mentioned these are of the insides of the Z80 pod for the B2000A.
The 40 pin DIL header to plug into the target system is on the left in the images.

Thanks Trev for posting this. It's interesting that they appear to have just put the original B2000 'Personality Module' in a box, directly on the cables with not even the expense of a main 'carrier' board to plug these into.
- Just as they'd done on the rather bodged with lots of wires on the 8085 (Personality Module in B2000) to 8031 (IC) converter, that Jeremy had and posted here: https://www.eevblog.com/forum/testge...=1772318;image

Co-incidentally, I was considering doing the same for my B2000A unit (especially as I recently found a couple of short DIP40 IDC cables, to save me making one side up). But I was also thinking of maybe securing the cables at the right pitch with pin-headers going through plain matrix-board, so that 'Personality Boards' could be just plugged into these (like with original unit - as well as the Dataman Microdoc IIRC) and save the space to store / extra cost of having to make up several external boxes for the different processors.

Originally Posted by SiriusHardware

I wonder how much that 'box with a 74LS74 chip in it' originally cost? I shudder to imagine. Looks like that ought to be really easy to reverse - engineer if you were able to take a look at the other side of the PCB as well.

Graham, No need to rev-eng this - Polar actually published the connection details in the original B2000 User Manual, attached in previous posts!
- And ironically (considering the main B2000(A) unit is Z80 based), the Z80 one is the only one that needs the extra ('clean-up' re-timing? D-type IC), with all the others just being a passive connection re-mapper (Plus the odd resistor network, for Pull Up/Downs?)

Although it would be interesting to know how much the ready-made boxed pods for the later B2000A unit / the 'Personality Boards' used within this (and fitted directly inside the original B2000) did originally cost, as well as price for the main unit - I'm yet to find a price list / advert for these anywhere. However, I don't think the Polar ToneOhm that was popular in Test & Repair departments (and they still sell a version of it), was particularly expensive (I've got a couple of older ones, I got v.cheap - Although I need to make-up a set of 'Kelvin' connected probes to 5pin DIN-plug leads for one unit, that was missing these)

[ortek_service]

Originally Posted by ortek_service

From: https://www.vintage-radio.net/forum/...1&postcount=33

I'm not sure if that should have been 'Zicon', but I spotted an L.J. Electronics SA2 Logic Analyser unit at a recent radio rally, and noticed this has 'Zicon' on the EPROM's labels as well as on the PCB's silk screen.

So this may actually be made by 'Zicon'?
I've not really found much about L.J.Electronics online - Only a mention in this Electronics mag priduct news pages:
https://worldradiohistory.com/hd2/ID...-01-IDX-52.pdf
But there is a manual for an SA1 (Predecessor?): https://www.opweb.de/english/company...ectronics/SA_1
Plus an SA3 (successor? with LCD) model on a certain online auction site for around $60, but won't ship to UK).

And I don't recall ever seeing one of these before, which appear to be based mainly around MC68xx
- See attached photos I took (Also attached zipped-up, to avoid compression).

I might be tempted to try and buy the one I saw if I see it again, as the same seller has been at many recent rallies
- Although it was the first time I'd noticed this unit at one.