HP 68302 User Manual page 121

Problem: Whenever you break into the monitor you have problems
with the SCC portion of your program.
Cause: The emulator asserts the FRZ pin when it breaks into the
monitor and this in turn "freezes" the Communications
Processor. Based on what type of SCC setup you have, and
what type of activity is occurring at the time of the break,
you may experience unexpected SCC errors or activity.
Note that if you are using the background monitor the FRZ
is asserted during the entire time the emulator is running
in the monitor. If you are using the foreground monitor,
the FRZ pin is asserted for a short time during transition
from your program to the monitor program (approximately
30 CPU cycles).
Fix: Either use the foreground monitor, which will reduce but
not eliminate the time that the FRZ pin is asserted, or
avoid setting any breakpoints while debugging SCC
functions. By using the trace analyzer, you can capture a
real-time log of SCC-related bus activity.
Problem: You are using the DRAM refresh controller of the 68302,
but when you break into the monitor, the values in your DRAM
become corrupted.
Cause: You are either using the background monitor, or have not
made the proper modification to the foreground monitor.
Fix: Use the foreground monitor and include the necessary
modifications. Refer to "Step 7. If you use the 68302
built-in DRAM refresh" for details on how to ensure proper
DRAM refresh.
Chapter 4: Plugging the Emulator into Target Systems
Configuring the Emulator for In-Circuit Operation
121