KM11 uPB question

Fritz Mueller fritzm at
Fri Jun 24 17:38:05 CDT 2016

Hey folks,

While working on my 11/45, I built up a KM11 replica based on Tom Uban's 
ExpressPCB layout.  I noticed the following behavior when trying to use 
it in uPB mode on my KB11-A CPU:

  * If I set up uPB, set KM11 S1 on and S2 off, and resume execution,
    the breakpoint fails to stop the processor
  * BUT, if I depress and *hold* CONT, while it is held down the CPU
    will be held in T2 on the target microword
  * If I then reach over and flip on S2 before releasing CONT I can hold
    the machine there in T2

Documentation on the KM11 seems to imply that the machine should just 
stop at the target state holding in T2 without having to do the 
holding-down-CONT-while-flipping-on-S2 thing.

I was wondering if this was an oddity of my KM11, my CPU, or is that 
just the way uPB mode works on these things?


More information about the cctech mailing list