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Bad Code
Remember, the one variable that is always changing in this set up is the code itself! If you keep a baseline
code image on hand that is known to work, you could always load that image into the emulator as a sort of
sanity check.
Bad Target Hardware
Try running the target from an EPROM that contains known good code to see if the hardware functions
without the emulator. This is always a good sanity check if things just stopped working and the ‘Bad Code’
suggestions above did not help.
Arbitration Time-outs
Arbitration time-outs are reported when Flex ROM III was unable to complete a memory access within
about 65 us. This can only happen if arbitration has been enabled. If you did NOT intend to do arbitrated
accesses, remove the “/A” parameter from the loader command line or turn on the “RESET during
DOWNLOADS” option in Quickloader. If you truly meant to do arbitrated accesses to the memory space
while the target is using that same space, verify the following:
If you are using READY arbitration, the emulator MUST see target activity to properly arbitrate with it. If
the target is not accessing the memory space emulated by this emulator, it will not see activity and therefore
will not be able to arbitrate. The emulator must see ACTIVITY (both start of accesses and end of
accesses). Also note the /READY line uses an open collector driver and provides a very weak pull-up
resistor. If the target does not provide a pull-up at the connection point, you may need to add a 1K - 10K
resistor between the connection point and your target’s VCC to improve rise times.
If you are using REQUEST/GRANT arbitration, verify that the target arbiter is working, both /RESET and
/GRANT are properly connected and that the target arbiter expects an active LOW /REQUEST and
generates an active LOW /GRANT (if using FEGRANT) or an active HIGH GRANT(if using REGRANT).
Also note that /REQUEST is an open collector driver to allow multiple emulators arbitrate in parallel. If
your target does not provide a pull-up resistor at the attachment point, you may need to add one (around
10K should do).
If you are using CYCLE INTERLEAVING arbitration, verify that you set the arbitration option to READY
mode and left the ready line disconnected. Also verify that the target cycle time is at least 300ns. This is
measured from the END of one cycle (CS, OE or WRITE going INACTIVE) to data stable requirement in
the next cycle.
If you are using Cycle Paralleling, verify that the selected ‘grant’ signal truly indicates that the target will
not expect data from the emulator for at least 300ns. You could verify this with a 2 channel scope. Trigger
one channel on the selected ’grant’ signal. Connect the 2 nd channel to the emulator’s chip select line. If the
two NEVER go active at the same time, or if there is always at least 300ns between the start of the ‘grant’
signal and the start of the emulator chip select, then it should work.
FlexROM III User’s Manual
30
Copyright ? 2001, TechTools
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