HP 64746 User Manual page 176

Chapter 5: Plugging into a Target System
Configuring the Emulator for In-Circuit Operation
Fix:
PROBLEM: You get "ERROR: Monitor failure; bus error" when trying to do
a display, modify or load command.
Cause:
Fix:
PROBLEM: Whenever you break into the monitor, you have problems with
the SCC portion of your program.
Cause:
Fix:
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:
176
Make sure the stack pointer is pointing to a legitimate address
and that any chip-selects for that address are initialized.
This error means that when the emulator tries to read from or
write to a memory location mapped as target RAM or ROM, a
bus error exception occurred. This can have many causes, but
most often is caused when you try to access memory that relies
on a chip-select signal, but have not initialized the chip-select
registers first.
Make sure that your chip-select registers are properly initialized.
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).
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.
You are either using the background monitor, or have not made
the proper modification to the foreground monitor.