HP 64783A, User Manual

Page: 666 / 816

r rst
6 Verify correct operation of the target system.
An example of a target system that requires an additional reset circuit is one that
normally has RAM starting at address 0, but for the first two bus cycles after reset,
maps ROM to this area instead to provide the inital vectors. If this remapping does
not occur, the system will attempt to fetch these vectors out of RAM, which will
fail.
For systems that require additional circuitry to be initialized by reset, a reset output
from the emulation probe (called reset flying lead) is provided. This reset flying
lead can be connected into your target circuitry to eliminate the need for an
additional step to reset circuitry in your target system. This allows the whole reset
procedure to be controlled by the emulator, automatically.
One additional thing to keep in mind is that your target system can initiate a reset
without the knowledge of the emulator. A reset that is initiated by your target
system will reset the emulator. If the emulator was running your target program at
the time of the reset, then when your system releases reset, the emulator will run as
if an r rst command had been issued. If the emulator was executing in the monitor
at the time of the reset, it will return to the monitor when the reset is released.
Another resetting method that may provide more convenience than the first method
requires use of the monitor. This method works well for target systems such as
those in the example above. This method resets the emulator into the monitor
instead of running the target system program immediately. Once in the monitor,
the initial stack pointer and initial PC can be loaded into the appropriate registers,
and then a run of the target program can be initiated. This method will be
illustrated in the next section.
Chapter 18: Connecting the Emulator to a Target System
Installing Emulator Features
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