Odd-looking scope trace on an address line

dwight dkelvey at hotmail.com
Wed Feb 8 15:14:57 CST 2017

How many vo;ts per division are you using?

It doesn't look like an issue but with out some reference

I don't know what to say.


From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Adrian Graham <witchy at binarydinosaurs.co.uk>
Sent: Wednesday, February 8, 2017 12:45:23 PM
To: Discussion: On-Topic and Off-Topic Posts
Subject: Odd-looking scope trace on an address line

Hi folks,

Clear one problem and hit another is just what I expect to happen with this
Executel :)

After last weekend's little breakthrough my little machine is now hitting a
loop that LOOKS like it's waiting for an RST6.5 interrupt*, but at the same
time the A9 line is doing this:


(scale doubled for ease of viewing)

That doesn't look normal to me, but all 8 chips that touch A9 check out OK
and there's nothing odd resistance wise.

Before I start chasing my tail again I thought I'd ask first...

(*for anyone interested RST6.5 is triggered by the TS1/TS2 status lines from
the MR9735 teletext decoder and should be constantly active while video is
being output. At one point Tony suggested this chip needs to be initialised
and there is indeed a control word that can be passed to it to turn it on
and off which makes me wonder if there's another memory bit stuck somewhere)


Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer

More information about the cctech mailing list