Blinking Light program for PDP-11

From: Tom Uban <>
Date: Thu Dec 2 12:07:33 2004

Hi Ashley,

Did you get a response on your question? One point
to keep in mind is that the various processor types
behave slightly differently. The typical method used
to do the "Cylon" lamp effect was to use the console
switch/display register (777570). A pseudo code program
would be something like this (translation left as an
exercise for you:-):

         Write '1' to console display register.
Lamp Loop:
         Load spin count into register 2.
Spin Loop:
         Decrement register 2.
         Branch if non-zero to Spin Loop.

         Rotate the console display register value left.
         Branch to Lamp Loop.

This code will continually rotate one lamp from right to
left across the display. A more complex version would switch
directions when the lamp hits either end.

Now for the problem. Only some processors (45, 70, perhaps
others, but I don't think the 35 or 40) support display of
the console switch/display register.

There may be some other more generic method that works on
all processors, but I'm not sure what it might be...


At 10:01 AM 12/1/2004 -0500, you wrote:

>I seem to recall seeing a little program that
>can be toggled into a PDP-11 (35/40/45/etc) that
>will create a "rolling lights" pattern on the
>front panel console, where the lights roll to the
>right and left, off and on. Can anyone here on
>the list point me to that program? I know that I
>saw it somewhere on the internet. I'd like to
>toggle that program in on my system.
>On another note, I got my ASR-33 working, connected
>online via 20mA DZ11 connection to my 11/34. I had
>the send/recv wires crossed. It works perfectly now.
Received on Thu Dec 02 2004 - 12:07:33 GMT

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