Print Page - LED on PET motherboards.

Title: LED on PET motherboards.
Post by: Shaun_CCC(UK) on August 20, 2010, 01:11 AM

Hi,

We're working on a restoration project for the National Museum of Computing here in the UK (http://www.tnmoc.org) and we were wondering what the red LED is supposed to do when you switch the machine on? Is it supposed to flash, light up, light up during boot up etc...???

Can anyone help please?

Regards,

Shaun.

Title: Re: LED on PET motherboards.
Post by: pet1978 on August 20, 2010, 05:42 AM

Hi

The LED will only light when running Commodore's diagnostic software. It is turned on by a normally unused keyboard scan-line value. Official Commodore dealers had a small box that was clipped onto the CPU which contained the diagnostic software in ROM.

Schematic (LED is near bottom right corner, driven from E9 NAND gate): http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/320130-1.gif

Dave

Commodore 128 Alive!

Commodore PET => Commodore PET => PET hardware => Topic started by: Shaun_CCC(UK) on August 20, 2010, 01:11 AM