Blinking Light program for PDP-11

From: Ashley Carder <>
Date: Thu Dec 2 12:32:37 2004

>Tom Uban wrote:
> 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...

Hi Tom,

I got a little "single rotating bit" program, coutesy of Guy Sotomayor,
who's been a *BIG* help to me. I used this little program to do some
basic testing on my PDP-11/40. It continually rotates one lamp across
the display. This program was loaded as follows:

Load address 001000
Deposit 005000
Deposit 005200
Deposit 006100
Deposit 000005
Deposit 000775
Load address 001000 and press Start.
You should see a bit rotate around on the data LEDs.

If anyone has any more interesting programs that can be toggled in
for "blinking light" effects, I'd be interested in trying them out.

After toggling in a couple of these types of things with the front
panel last night, I decided to move on to bigger things. I hooked up
an RL02 and was able to successfully boot RT11 v5.3, XXDP 2.5,
and my Wofford Witch RSTS/E v7 system.

Life is good!!!

Received on Thu Dec 02 2004 - 12:32:37 GMT

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