6522 (and maybe others) tester.

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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bprosman
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6522 (and maybe others) tester.

Post by bprosman » Sun Jun 02, 2019 9:48 pm

Is it possible to create a 6522 tester using an FPGA (EEPizza) or CPLD ?
I have a whole bunch of these, some of them are from the "C64 Speeddos days" so most probably a blown up port.
Some functions can be tested by plugging it into an Atom or BBC but that is still no guarantee.

I have a BBC where 2 6522's had an issue and couldnt be interchanged so something was broken.

Just an idea... a test program in the Atom could also be a solution of course.


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Elminster
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Re: 6522 (and maybe others) tester.

Post by Elminster » Sun Jun 02, 2019 10:06 pm

Interesting. We have the ICE-T that replaces CPU, Perhaps the ICET 6522 Edition.

But then a tester that tested 6522s and 6502 would be good.Would also make buying 65x2's from ebay slightly more comforting. (You can of course buy new ones but where is the fun in that)

I expect Hoglet has probably already had some thoughts around that.

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Re: 6522 (and maybe others) tester.

Post by bprosman » Sun Jun 02, 2019 11:10 pm

a tester that tested 6522s and 6502 would be good
And the 8255, 6845 and 6847 without being greedy :mrgreen:

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tricky
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Re: 6522 (and maybe others) tester.

Post by tricky » Mon Jun 03, 2019 5:54 am

I'm sure that someone from the UK arcade community WS working on an FPGA logic chip tester - speed and voltage, but I don't think the plans stretched that far.

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Re: 6522 (and maybe others) tester.

Post by bprosman » Mon Jun 03, 2019 7:17 am

Logic chips (74xx and 40xx) is not such an issue, I can use my TL866 for that.

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JudgeBeeb
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Re: 6522 (and maybe others) tester.

Post by JudgeBeeb » Mon Jun 03, 2019 7:38 am

I don't think this would be 'difficult' in the conventional sense. Indeed, an FPGA would probably be overkill. If we are talking about relatively slow (by today's standards) 5V tolerant logic devices, it should be possible to develop something just using a micro-controller.

The difficulty would be working out what to do to each pin to test them and what I imagine would be fairly laborious code for each of the pins. I am also not sure how re-usable the code would be between different logic devices.
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Re: 6522 (and maybe others) tester.

Post by bprosman » Mon Jun 03, 2019 8:12 am

The difficulty would be working out what to do to each pin to test them and what I imagine would be fairly laborious code for each of the pins. I am also not sure how re-usable the code would be between different logic devices.
For the simple I/O tricks it wouldn't be that difficult, but it gets exciting in case of an e.g. 6522 when you come to counter/timer interrupts etc.

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Re: 6522 (and maybe others) tester.

Post by daveejhitchins » Mon Jun 03, 2019 11:15 am

I'm sure, with a little glue logic, you could just hang a test jig off the User Port or 1MHz Bus ??

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tricky
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Re: 6522 (and maybe others) tester.

Post by tricky » Mon Jun 03, 2019 1:41 pm

I think the idea of the FPGA was to test response times to various logic levels.
Unless you want to see if your cheap 2mhz 6502 is actually a rebadged 1mhz one, it probably isn't worth it as you say; and even then, a microcontroller with something to give enough io pins or pi-zero would probably be up to the job.

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1024MAK
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Re: 6522 (and maybe others) tester.

Post by 1024MAK » Mon Jun 03, 2019 3:02 pm

bprosman wrote:
Sun Jun 02, 2019 9:48 pm
Is it possible to create a 6522 tester using an FPGA (EEPizza) or CPLD ?
I have a whole bunch of these, some of them are from the "C64 Speeddos days" so most probably a blown up port.
Some functions can be tested by plugging it into an Atom or BBC but that is still no guarantee.

I have a BBC where 2 6522's had an issue and couldnt be interchanged so something was broken.

Just an idea... a test program in the Atom could also be a solution of course.
Is it possible - yes.

Is it worth it? That’s an entirely different question.

Unless someone wants a ‘because I want to prove it myself’ reason, I don’t see many being interested given that brand new 6522 and good used ‘pulls’ are still available. The new 6522s are a reasonable price.

As you indicate, the easiest option is to fit a suspect 6522 in a BBC B. If the system will not run when the suspect 6522 is put in the ‘system VIA’ socket, it’s toast. If the system runs with the suspect 6522 in use, it’s almost certainly fine.

Same with 6502s. If it works in a Atom, a BBC B or an Elk, it’s almost certainly fine.

Mark

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Re: 6522 (and maybe others) tester.

Post by bprosman » Mon Jun 03, 2019 3:35 pm

As you indicate, the easiest option is to fit a suspect 6522 in a BBC B. If the system will not run when the suspect 6522 is put in the ‘system VIA’ socket, it’s toast. If the system runs with the suspect 6522 in use, it’s almost certainly fine.
Do not completely agree with this, as I have a BBC B, and I have 6522's that do work in one of the 6522 sockets and not in the other. It does work in an Atom but not all ports are ok. So assuming the device is 100% ok when it makes a BBC B or Atom startup is not correct as not all functionality is always fully used. Especially not if you go into the timer/counter/interrupt area.
new 6522 and good used ‘pulls’ are still available.
Also true but I have 20...30 laying around I dont 100% trust. Of course I can throw these in the bin and buy new ones, they will be ok , but the "pulls" is also questionable.
Especially in a new design you want to have "trustworthy" / tested devices.

Found some material/ideas :
http://sleepingelephant.com/ipw-web/bul ... php?t=8301
Last edited by bprosman on Mon Jun 03, 2019 3:40 pm, edited 3 times in total.

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Elminster
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Re: 6522 (and maybe others) tester.

Post by Elminster » Mon Jun 03, 2019 3:58 pm

I think the crux of it is how to reliably test 100% a 6522. I have also come across 6522 that seemed to work fine in some instances and not in other machines. Possibly tolerances involved.

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1024MAK
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Re: 6522 (and maybe others) tester.

Post by 1024MAK » Mon Jun 03, 2019 4:09 pm

bprosman wrote:
Mon Jun 03, 2019 3:35 pm
Do not completely agree with this, as I have a BBC B, and I have 6522's that do work in one of the 6522 sockets and not in the other. It does work in an Atom but not all ports are ok. So assuming the device is 100% ok when it makes a BBC B or Atom startup is not correct as not all functionality is always fully used. Especially not if you go into the timer/counter/interrupt area.
The ‘user VIA’ is not used by BASIC or the OS. So, unless you write some software to make use of it (test it), and attach some hardware to the printer port and user port, trying a suspect 6522 in this position is not very meaningful.

A substantial, but not complete use is made of the facilities of the 6522 in the ‘system VIA’ position. So, yes, a suspect 6522 that works in this position does not prove that it is 100% okay, I agree. But it is a quick and simple test
bprosman wrote:
Mon Jun 03, 2019 3:35 pm
new 6522 and good used ‘pulls’ are still available.
Also true but I have 20...30 laying around I dont 100% trust. Of course I can throw these in the bin and buy new ones, they will be ok , but the "pulls" is also questionable.
The used chips I was referring to, were those available from a member here, not the Wild West of eBay etc...

If you have 20 to 30, then that is a bit different to having a handful of less than say five or six.

As others have said, either using a microcontroller, or indeed an Atom / BBC B ( using a known good 6522) to control and monitor the suspect 6522 is certainly the easiest way to do this.

With an Atom or BBC B, connect the suspect 6522 address, control and data bus lines to the expansion bus / 1MHz bus and then use the known good 6522 to feed test signals to, or monitor output from the suspect 6522.

Mark

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Elminster
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Re: 6522 (and maybe others) tester.

Post by Elminster » Sun Jun 09, 2019 12:15 am

Has anyone looked at the Arduino Vidor? A bit expensive but wondering if that would be easier to learn, and could be used for such a project as above.

bprosman
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Re: 6522 (and maybe others) tester.

Post by bprosman » Sun Jun 09, 2019 8:32 am

Nice board but for testing the Arduino Mega2560 should be sufficient.

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Elminster
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Re: 6522 (and maybe others) tester.

Post by Elminster » Sun Jun 09, 2019 9:19 am

I thought you wanted to use a FPGA :) or did you change your mind?

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Re: 6522 (and maybe others) tester.

Post by bprosman » Sun Jun 09, 2019 9:45 am

Would prefer that but lacking FPGA skills, so might go for an Arduino.

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Elminster
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Re: 6522 (and maybe others) tester.

Post by Elminster » Sun Jun 09, 2019 9:49 am

bprosman wrote:
Sun Jun 09, 2019 9:45 am
Would prefer that but lacking FPGA skills, so might go for an Arduino.
That was why I thought the Arduino with built in fpga would be ideal. Same environment. Tempted myself but time lacking.

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