PDP 11/45 Display register.

[John A. Dundas III]

Almost.

The SR and the DR are at the same memory location.  Reading gives the 
switch settings (the low 16 bits worth), writing sets the display 
register, assuming the Data Display Switch is set correctly.  You 
cannot read back what you have written, you will always get the 
switch settings.

Can't say if you have a fault or are doing something incorrectly yet. 
Not certain you can set the display register from the console. 
Someone with a live /45 might check that.

John

At 9:45 PM +0200 4/5/05, Gooijen H wrote:
>   Well, let's try to give an answer.
>The SWitch Register is what is says: *switch* register.
>So you can read the switches from it, but writing to it is no use.
>Don't shoot me if I am mistaken!  From memory, the address is 777570.
>
>- Henk, PA8PDP.
>
>
>-----Original Message-----
>From: cctalk-bounces at classiccmp.org
>To: Classic  computer list
>Sent: 5-4-2005 21:33
>Subject: PDP 11/45 Display register.
>
>Hi,
>
>A quick question raised by my ongoing work....
>
>Is it possible to write directly to the "display register" - the one
>accessed by one position of the data switch. I think it should be at
>memory
>location 777570, but I can't get data into it, either using deposit from
>the
>console, or moving data under program control.
>
>Have I got a fault, or am I doing something wrong?
>
>Thanks
>
>Jim.
>
>Please see our website the " Vintage Communication Pages" at
>WWW.G1JBG.CO.UK