Testing 6522 chips

[kakemoms]

Hi

I need to test some 6522 chips and after some discussion I droodled down this schematic:

and in monochrome

The basic idea is that I want to test its functionality, but also record the waveform of the different outputs to see that the chip is "within spec" or what parts of the chip that is actually such.

If you have any feedback on testing of such chips (or experience) I would like your comments/idea on this.

[BigDumbDinosaur]

kakemoms wrote:

Hi

I need to test some 6522 chips and after some discussion I droodled down this schematic:

Tester6522.png

The basic idea is that I want to test its functionality, but also record the waveform of the different outputs to see that the chip is "within spec" or what parts of the chip that is actually such.

If you have any feedback on testing of such chips (or experience) I would like your comments/idea on this.

Could you please post that in monochrome?

[kakemoms]

BigDumbDinosaur wrote:

Could you please post that in monochrome?

I have added a monochrome version now.

[BigDumbDinosaur]

kakemoms wrote:

Hi

I need to test some 6522 chips and after some discussion I droodled down this schematic...

Reset is floating on the 65C22. You need to pull it up to Vcc or make arrangements to have the Arduino positively drive it, preferably toggle it at power on.

Also, does your Arduino logic observe the requirement that the 65C22's chip selects and R/W be valid before the rise of Ø2?

[GARTHWILSON]

I've been careful about anti-static handling precautions, and the only '22 I've seen go bad apparently had a bond wire come loose on one of the I/O lines, making an open circuit. That was on one of our products that we sold from 1994-2007. On the workbench computers and breadboards, I've never seen one go bad, except there was one time many years ago that I accidentally let a screwdriver roll under the main workbench computer while it was powered up, and it shorted a bunch of the wire-wrap pins together and blew something. I never bothered to troubleshoot it. I think I just replaced all the ICs and got going again.

In my first build with a '22 though, I got tripped up by the very thing BDD is saying. The chip selects and R/W have to be valid and stable before Φ2 rises. IOW, you can't use Φ2 to gate the chip selects.

[GARTHWILSON]

I'm not familiar with the Arduino, but it looks like you have the Φ2 input of the '22 connected to an input on the Arduino. Hopefully that pin can be an output too and you're using it that way.

It would be a good idea also to send a signal to CS2\ rather than just grounding it, to make sure it really works.

Thanks for the monochrome diagram. I don't have color-blindness problems like BDD (I think he said the light green is almost invisible against the white background), but that light-gray writing labeling the pins is awfully hard to read. Eagle apparently allows you to change the colors, but I wrote to them and asked them to supply it with defaults that are easier to see.

[DerTrueForce]

I believe that most pins on an Arduino can be used as digital I/Os. I've only ever used a Uno, but the pins marked as analog inputs on that can be individually set to digital inputs or outputs, if required.