XXDP on PDP-11/03

Douglas Taylor dj.taylor4 at comcast.net
Wed Aug 14 10:25:39 CDT 2019

On 8/14/2019 10:17 AM, Noel Chiappa via cctalk wrote:
>      > From: Paul Koning
>      > Isn't the interrupt disabled by RESET?
> Nope. On the -11/03 and KDF11-A, BEVNT is wired straight into the CPU, and
> there's no internal register to control it.
> The BDV11 does have a register which can enable/disable the LTC (it connects
> BEVNT to ground via a transistor when the appropriate register bit is
> cleared); but, ironically (given your question), BINIT/RESET does _not_ clear
> that register! Only BPOK does. (My theory is they were short of a bus receiver
> for BINIT, and rather than put a whole extra chip on the card...) So, once on,
> it has to be explicitly turned off, or the 'boot' switch (which toggles BPOK)
> has to be hit.
> The KDF11-B and all KDJ11 machines do have the LTC register, which operates
> 'correctly'.
> 	Noel

Everyone was right about what I was experiencing.  It was BEVNT/LTC.  
The front panel switches on the BA11-M I have read:


and I can't turn off the LTC from the front panel.  I had to set a 
switch on the BDV11 to disable BEVNT and with that XXDP booted up.  
Version 2.6.

Would like to run the RXV21 diagnostics since I have a 2nd controller 
that fails to work with the RX02 emulator.


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