Re: A newly working Commodore 720 - many questions...

From: Ethan Dicks <>
Date: Thu, 16 Feb 2012 12:50:45 -0500
Message-ID: <>
On Thu, Feb 16, 2012 at 12:37 PM, Rob Clarke <> wrote:
> Wow - so many options. I like the option of a single chip solution from
> Gerrit as it doesn't require opening the PSU or attaching or hooking up to
> mains voltages. Incidently, the MAX machine used a 555 to generate the TOD
> signal, as Uz speculated.

There used to be an 8-pin DIP that was commonly used in the 1970s for
generating 60Hz using a 32768Hz watch crystal.  These days, it's often
done with an 8-pin PIC or AVR.  I don't remember which part I used,
but I made one about 5 years ago, since I needed to run an 8051-based
clock off of DC and the design had a diode and a 74HC14 off of the
low-voltage AC side of the rectifier.  I remember it being moderately
accurate.  For that matter, unless you are using your PET as a desk
clock, a 555 is probably accurate enough for casual use, and it's hard
to get cheaper than that.


       Message was sent through the cbm-hackers mailing list
Received on 2012-02-16 18:00:16

Archive generated by hypermail 2.2.0.