Step 4. Know Your Interrupt Mode - HP 64746 User Manual

Chapter 5: Plugging into a Target System
Configuring the Emulator for In-Circuit Operation

Step 4. Know your interrupt mode

If your target does not use dedicated mode interrupts, you can skip this step.
One of the more common problems users encounter is not being able to break into
the monitor (ERROR: break failed). A common cause of this is configuring the
emulator for dedicated mode interrupts, but failing to ensure that the 68302 is
programmed for dedicated mode interrupts.
The emulator is configured to use normal mode interrupts by default. If you will be
setting up the 68302 for dedicated mode interrupts, you should answer the
configuration question:
with the choice "dedicated".
The interrupt mode of the 68302 is determined by the value programmed in the
GIMR register. If you are using dedicated mode interrupts, you must set the most
significant bit of the GIMR register BEFORE you attempt to step or break. Similar
to setting up chip-selects, you have two options for making sure you have a valid
interrupt mode:
Method 1: Using a Command File to Set the Interrupt Mode
Use a series of commands or a command file that modifies the GIMR to force the
68302 to be in dedicated mode. For example, here is a command file that sets up
the GIMR for dedicated mode:
reset <RETURN>
break <RETURN>
modify register r302 bar to 800H <RETURN>
modify register interrupt gimr to 8700H <RETURN>
It is important that you first modify the BAR register BEFORE attempting to
Note
modify the GIMR register because the location of that register is calculated based
on the value in the BAR.
Note that doing a break when the 68302 is in a reset state does not require a level 7
interrupt, and therefore will work regardless of the interrupt mode setting.
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Interrupt mode?