PDP-12 Restoration at the RICM

Michael Thompson michael.99.thompson at gmail.com
Mon Jun 15 18:42:42 CDT 2015

> Date: Mon, 15 Jun 2015 05:01:36 +0000
> From: tony duell <ard at p850ug1.demon.co.uk>
> Subject: RE: PDP-12 Restoration at the RICM (tony duell)
> >
> > Tony, thank you for your offer to supply replacement M452 Variable Clock
> > modules for the console. We already have one jumpered for 110 baud for
> the
> > Teletype. The other two M452 modules should be jumpered for 9600 baud and
> > 38400 baud. The second serial port uses a M405 Crystal Clock module with
> a
> Do you want 3 separate modules, or one switchable, or what?
> > different pinout and clock outputs than the M452. We don't have any of
> > these modules, so the three that we need should be jumpered for 110 baud,
> > 9600 baud, and 38400 baud. The shipping address for the RICM is on the
> > page.
> Hang on. I thought the M405 was just a crystal oscillator without a
> divider. Are
> you sure there is no extra division on other modules? 110Hz is very slow
> for
> a crystal oscillator, after all.
> -tony

The M452 creates a 110 Hz clock for the TTY transmitter and a 880 Hz clock
for the TTY receiver.
The M405 for the DP12-B serial port generated a clock that is 16x the baud
rate which is then divided by an M216 module.

Michael Thompson

More information about the cctech mailing list