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Are there modifications of Atmel EVBs for using Nexus trace?
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| Ref: 0366 |
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To be sure that trace signals on the EVB are really released and available for Nexus trace,
the system offers a diagnostic command. Just enter:
DIAG 3016
The result will be displayed in the AREA window.
Possibly for the following EVBs, modifications are needed to be able to use Nexus trace:
EVK1101 :
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Check if the Push button SW4 and SW5 are really open. ? (PB3 -> MDO4, PB2 -> MDO3).
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Check if the pins 1 till 6 of J17 area really open.
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R32 (0 Ohm) must be removed if U7 is populated. (PB4 is MDO5).
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EVTI : R33 (0 Ohm ) must be removed if U7 is populated.
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PB0 and PB1 are connected to the SD-Card Socket. Remove SD-Card!
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J16 pin 18 must be N/C.
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PA31 (MDO0) is connected to the temperature sensor.
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J16 pin 17 must be N/C.
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Be aware that PA30 (MCKO) is connected to the Photo sensor.
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Is a breakpoint instruction allowed in the code?
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| Ref: 0376 |
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Breakpoint instructions are not allowed in code if a debugger is used for debugging.
Without a debugger, a breakpoint instruction is executed as a NOP instruction. In this
case, the code will work anyway.
If a debugger is involved , program execution will stop at the breakpoint. The user program will not work.
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Which impacts regarding real time behavior must be expected if the Nexus trace is activated?
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| Ref: 0372 |
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As long as just program trace is activated and MCKO is set to CPU clock, no speed impacts must be expected.
In special cases , just Flowerrors may be visible in the trace list window which may cause flow lost in the trace
list. But there is still no speed impact of real time program execution.
In case of slower MCKO (1/2, 1/4 etc. CPU clock) and in case of data trace is additionally activated, also no speed
impacts can be recognized. However the trace contents is possibly not usable due to not sufficient or wrong
information from the Nexus cell of the device.
To be able to get correct trace information from the device anyway, there is an overrun control register which allows
either to generate over flow messages or to avoid nexus FIFO overruns.
(Nexus FIFO overruns normally cause unusable trace buffer contents)
This mechanism however, may causes real time program execution impacts for the case, the Nexus FIFO
threaten to overflow. How much it depends on the user program and if data-rd and/or data-wr
messaging is enabled.
(This is not a problem of the debugger, but of the device)
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