HP 64783A, User Manual

Page: 681 / 816

Installing the foreground monitor
The foreground monitor supports all features of the emulator, but imposes on your
target system more than the background monitor. The foreground monitor occupies
a 4-Kbyte block in your target memory space. The emulator provides memory for
this 4-Kbyte block, but the target system cannot use this address range for anything.
The cycles strobes TS and TIP are shown to the target system during foreground
monitor cycles. The monitor needs to be placed in an address range where it will
not interfere with target system operation.
If the monitor is placed in an address range where the target system responds with a
TA, interlock the monitor to the target strobes. The target system must not respond
with TEA for this address range. If the monitor is placed in an address range where
the target system does not respond with any strobes, do not interlock the monitor.
If in doubt, interlock the foreground monitor to the target system. It will be
obvious if this is the wrong thing to do because the monitor will stop operating
immediately.
If the MMU is being used, the monitor must be placed in an address range that is
translated logical=physical, and is writeable for supervisor program and data. If the
memory management scheme is dynamic, the monitor page must be resident at all
times. In addition, any pages required for stacking or vector fetches must also be
resident.
If there is not a suitable address range in which to put the monitor, the system
protection schemes may need to be modified to create a place for the monitor. This
may be as simple as adding an entry to the MMU tables, or it may require
modifying a hardware protection scheme to allow placement of the monitor.
Besides adding special requirements to the placement of the monitor, the MMU
impacts many operations of the emulator and processor. When the MMU is on, the
emulator can access both physical and logical memory. The emulator also provides
commands to examine the MMU tables.
With the MMU on, there are new problems added to the task of connecting the
emulator probe into a target system. Besides making sure that the restrictions noted
above are complied with, interpreting the trace list becomes more difficult. You
also need to keep in mind the distinctions between logical and physical memory
accesses when accessing memory. Finally, you need to find out whether you need
to load your program before the MMU is running or while it is running.
Chapter 18: Connecting the Emulator to a Target System
Installing Emulator Features
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