False positives? #14
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I finally had a chance to look at this. On the first setion, pattern scan: There are too many FOUND results. Even after I remove the results that could have been due to the loopback entries, there are still too many. It is not uncommon to have many "FOUND" results but typically you would see that at least the TDI, TDO and TCK pins remain constant. Having the correct ntrst pin is not always required and even the TMS pin may not be required if the target is already in bypass mode on reset. On your target in the FOUND results after removing loopback pairs, the TDI and TDO change too often to indicate proper JTAG found. Another issue with the results is that the IR length on the FOUND entries is often The next scan, IDCODE scan requires manually checking given output to see if they are actually valid IDCODE's and the results have a few entries worth investigating further. What is nice about the above entries is that the TCK, TMS and TDO are constant. Assuming the target chip starts with IDCODE its default register then you only need to find those 3 pins to read out the IDCODE. I could not find def parse(idcode):
manufacturer = idcode >>1 & 0b11111111111
part = idcode >>12 & 0b1111111111111111
version = idcode >>28 & 0b1111
print("mfg: 0x%3.3x, part: 0x%4.4x, ver: 0x%1.1x"%(manufacturer,part,version))
>>> parse(0xF901A003)
mfg: 0x001, part: 0x901a, ver: 0xfI really cannot imagine manufacturer 0x1 being valid? 0x1 would be an AMD chip (according to jep106.inc which is generated from the JEDEC list which you can find an unofficial copy of here ) A suggestion I could give would be to run the IDCODE scan a couple of times and compare the outputs to find entries that are consistent between scans. |
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I’m working on a Tricore chip. I feel like I read their “miniwiggler” device sets proprietary parameters that enable JTAG on the device. Here is a rookie question. I have a 10 pin connector but I know one of the pins is GND. Would I have negative results if I was including that in the possible A1, A2, A3 pin array? Also, how would I know if I need a resistor before this JTAG connector is usable? |
Does this mean I should unplug/unwire with A1, A7, or both? |
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Sorry for the delay. It depends. A true loopback would showup as something like You could read your results as "When sending known pattern through pin A1 the state on pin A7 changed between HIGH and LOW 38 times. This could be a result of stimulation sent on A1, could be the result of bad wire insulation on A7, could indicate that A7 is floating between HIGH and LOW on its own or that A7 is pumping out some sort of data or activity independent of stimulation on A1" |
It isn't clear to me which pattern is the actual pattern I'm interested in.
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