If the problem is not solved yet, something to look at before a re-boot. 
I'd say that (at the MPE level) LDEV 20 is hung. I recall many years 
ago, on the HP3000/70 series, running the old 16 bit MPE, there was a 
utility to reset serial port, a much bigger stick than ABORTIO, was it 
called TERMDSM? I'm sure there is a similar utility on your HP3000, and 
someone on the list know the name of it. If you do find this utility on 
your box you can use it for diagnostics on the ldev, or to just reset 
the ldev. DO NOT run it until you have shutdown all user processes. I 
recall that sometimes this utility would crash the machine during a 
reset ldev, but that was the series 70.

It sounds like the core I/O is bad,  ctrl-B works, ctrl-A doesn't work, 
and the machine is up.

Just to make sure you HP700/96 is configured correctly:
Set the HP700 terminal back to factory configuration as follows:

   1. Power off.
   2. Hold the "D" key down.
   3. Power on, continue holding the "D" key down.
   4. Release the "D" key when you hear the terminal bell.
   5. If no auditable bell after 15 to 30 seconds then repeat step 1 - 4.
   6. After the "D" key is release you should see a message in lower
      left corner of the screen, something about "Default Configuration
      Settings".
   7. Now, the Defualt baud rate may not match your system. Check the
      BAUD rate, make sure it is the same as the baud set for ldev 20 in
      sysgen.

my $0.02.......
Mike.

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