UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Computers


Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

Thread Tools
Old 26th Feb 2021, 10:11 pm   #701
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 5,700
Default Re: Non-working Commodore PET 3016

Originally Posted by ScottishColin View Post
OK - so if each 'large' horizontal line is 50ms, then I reckon about 1.35 x 50ms = 67.5ms between falling edges.

And the active CS pulse is about 0.1 * 50ms = 5ms.
Have another look. There are over two divisions between each falling edge, each division = 50mS so that's at least 100mS and more between falling edges. Try again.

The smaller ticks divide the large divisions into fifths, so one subdivision is one fifth of 50mS (=10mS). So how long is the active-low _CE pulse?

As to active low / active high, in the retro computer world chip select signals are usually (but not always) active low, that is they hang around up at logic 1 when inactive and only perform their designated function when taken low, to 0V.

There is a handy way to tell, when looking at circuit diagrams, whether an IC pin or a signal line is active low. If it is active low the pin or line name will have an 'overline' (as opposed to an underline) over the name. The attached close up of UD9 shows two signal or pin names which are active low, and one which is not.

In plain text like this, active-low signals are often indicated by putting an underscore in front of the signal name like this '_CS', or a forward slash, like this, '/CS'.
Attached Thumbnails
Click image for larger version

Name:	ActiveHigh_ActiveLow.jpg
Views:	31
Size:	52.7 KB
ID:	227747  
SiriusHardware is online now   Reply With Quote

Thread Tools

All times are GMT. The time now is 12:12 am.

All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at
Failure to heed this warning may result in death or serious injury to yourself and/or others.

Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.