Blinking Light program for PDP-11

From: Paul Koning <>
Date: Thu Dec 2 14:23:26 2004

>>>>> "Tom" == Tom Uban <> writes:

 Tom> Hi Ashley, Did you get a response on your question? One point to
 Tom> keep in mind is that the various processor types behave slightly
 Tom> differently. The typical method used to do the "Cylon" lamp
 Tom> effect was to use the console switch/display register
 Tom> (777570).

There are actually two basic approaches. The switch register one is
used by RT11. The other one relies on the fact that R0 is displayed
in the data lights when a WAIT instruction is executing. RSTS (and I
think the other OSs) use that.

Then there's the amazingly warped "fancy lights" option in RSTS, where
both the data AND the address lights rotate -- in opposite
directions. That one I'll leave as a challenge for the student. One
hint: it's only supported on machines that have supervisor mode.

Received on Thu Dec 02 2004 - 14:23:26 GMT

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