Oscilloscope timing pictures added to show ZX80 char process

[zx80nut]

Hi.

I've been doing some more work on documenting what happens within the ZX80 (and ZX81) hardware.
So, I have produced an annotated oscilloscope picture showing the major signals involved when doing the DFILE Opcode execute.
These are real scope pictures so that you can see the timing involved when reading, NOP injection, data latching etc.

Please note that a description of the timing shown on some other pages on the net is NOT the same as really happens on the ZX80.
I'll be adding some descriptive text shortly.
There is a link from my ZX80 page...
http://searle.hostei.com/grant/zx80/zx80.html
[Edit by Grant on 7th July 2012 - UPDATED URL !]

Opcode.jpg

ZX80 Opcode execution in DFILE

(157.4 KiB) Downloaded 3918 times

As always, please "refresh" the page in the browser to make sure you get the latest version. The link to the above picture is within the "Circuit Description" part of the page.

Regards.

Grant.

[sirmorris]

Fascinating stuff! What kind of scope are tyou using for that?

[zx80nut]

Hi.
It's a rather old (but brill) Telequipment D83. I have newer scopes, but the really stable delayed trigger and big bright display on it is much better than my newer ones.

The picure shown here is a collection of 10 images using exactly the same sweep trigger point.
I checked regularly between pictures to make sure the trigger point hadn't moved, so that I can be confident that all traces are shown accurately (they also match my "theoretical" traces that I drew on paper some time back).

These are then joined together with Photoshop, then I used Microsoft Visio to do the annotation.

Regards.

Grant.

[zx80nut]

An update: I've started to add description of the process to the page that shows the scope traces.

http://home.micros.users.btopenworld.co ... ePics.html

Bye for now.

Grant.

http://home.micros.users.btopenworld.com/zx80/zx80.html

[sirmorris]

Thanks Grant - I love this kind of stuff!