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Chapter 4: Connecting the Emulator to a Target System
Plugging The Emulator Into A Target System
If the "p>" prompt remains after target powerup, check:
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If the prompt is "c>", mechanical installation may be causing the problem, but the
most likely cause is a problem with the clock. If using a clock oscillator, check
EXTAL clock quality. Look at the voltage levels, edges, and duty cycle. If the
clock looks suspect, compare it to the target system clock without the emulator.
If the input clock is not the problem, check the CLKOUT signal. Is it operating
correctly?
If the prompt is "r>", either the target system never released the reset pin, or some
program error condition caused the target system to reset itself. If no bus cycles
were captured by the analyzer, the target system never released reset. You need to
find out which conditions must occur in order to release reset, and then investigate
those conditions to determine why reset isn't being released.
Consider the example of a multicard system whose design uses a master card to
start slave cards after verifying that they are installed in the system by reading
checksums from their ROMs. The reset of each slave card is released when its
checksum is read correctly. If the emulator interferes with the reading of the
checksum from one of the slave cards, its reset will not be released.
One thing to keep in mind is that the emulator does not trace alternate bus master
cycles while it is reset.
If any bus cycles were executed before the reset occurred, then something caused
the target system to reassert the reset condition. Usually, this is caused by some
type of fault detected by the system. Typical faults include the target system
attempting to access a restricted address range, or a watchdog timeout. Refer to
"Interpreting the Trace List", later in this chapter, to help understand what caused
the reset.
The default programming of the 6833x chip will cause it to periodically reset the
processor unless the watchdog address is appropriately accessed.
If the prompt is "b>", and there are no cycles in the trace list, the processor never
attempted to run any bus cycles even if other indications show it should have. This
could indicate problems with power, clock, or signal transitions, especially the
reset signal. Items to check include: - Check power supply voltage levels. - Make
sure the power up is monotonic. - Check clock quality. - Check that the reset
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mechanical installation of the probe.
blown fuses.
target system power supply voltage.
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