Hardware check sheet

[msknight]

I've been putting together a check sheet after going through various other comments and reading things.

I'd be grateful if someone could check the sheet, particularly the new sections for single RAM chips and 16k extended RAM chips to ensure I've got it right for the expected behaviour columns.

It's organised in two pages, so you can print two A4 sheets to cover a testing session - http://www.msknight.com/bbc/resource/CheckSheet.ods

[Lardo Boffin]

Any chance you can post these as PDFs as well please?

I can’t open ods files on my phone.

[msknight]

Sure - http://www.msknight.com/bbc/resource/CheckSheet.pdf

[siggi]

Pin 35 of ULA is the ocillator input:

ULA-35-OSC.jpg (4.79 KiB) Viewed 494 times

There should bei pulses @ 6,5 Mhz

Siggi

[msknight]

There should bei pulses @ 6,5 Mhz

Cheers! Keep 'em coming!

[1024MAK]

I've been putting together a check sheet after going through various other comments and reading things.

Okay. but keep in mind a couple of points.

First, pin 35 of the ULA is not a digital signal pin. It forms part of the master oscillator circuit. Hence connecting test equipment may affect the operation of the oscillator circuit. If the 3.25MHz signal is present and okay on pin 14, there is no need to test pin 35.

The second point is that you have to keep in mind that due to the way that the ZX81s video system works, the address and data lines can have different values on them depending on which chip pin you test.

For example, when the screen picture is being constructed by the system, the ULA grabs the data on the data bus from the memory, then overrides this data so that the processor sees a NOP instruction. Hence at this point in time, the value on the RAM and ROM will be different to that on the ULA and the processor.

The signals that you get also very much depends on what the system is doing. Often different signals from normal are a symptom rather than pointing to a definitive cause.

Mark