PDP-12 Restoration at the RICM - test-drb@ccmp.vtda.org

15 Jun 2015

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 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  WWW
  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