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Blackfin JTAG Not Detected on Custom Board (USB-ICE) BF514F


I'm having a problem on a custom board where when using the ADI VDSP++ Configurator the USB-ICE JTAG emulator does not detect a JTAG in its path when connected to our custom ADSP-BF514F board. I have a BF506F EZ Kit Lite to develop on and it detects this board just fine. I've attached my schematic/header pinout and layout. Note the pullup (R82) on pin one has been removed, and it is now shorted to ground

The traces are short <<6", although not exactly routed perfectly. It seems to me like this is a signal integrity issue, but for me it's hard to believe because the trace lengths are so short, and I don't have any clocks, or other used signal lines crossing over/under these traces. I didn't use any termination resistors because the traces are so short I didn't think it would be necessary. Also to note I have only included the minimum amount of components + a few more to allow for the board to be detected by the debugger--this includes: 25MHz oscillator, pullups on SDA/SCL, NMA#, RST#, pulldown on PG#, Bootmode is selected to boot from internal SPI Flash.

When probing the pins on the BF506F EZ Kit JTAG vs my custom board with a scope, TRST# looks fine (gets pulled up the same way), and there's not much to see on TDI/TDO (as far as I can see) since the configurator stops at "Determining scan path length" with the error "No JTAG devices detected in the scan path. Check target power and verify the JTAG signal integrity."

Could this be anything other than bad traces and lack of matching impedances on the traces? I noticed ADI suggests 4.7KOhm for pullup/down resistors (as well as saying no pullups on TMS, TCK, and TDI are necessary)--will that make a huge difference on signal integrity (I'd have to purchase these to test)?
  • Hi,

    The pull-up resistors that you have , although not needed, are not the cause of the problem that you are having. Most of the times, the reason that JTAG does not detect the device might not be from JTAG interface. If the target (DSP) is not powered right, the emulator will not be able to communicate with the DSP. Please check the possibility of the DSP not being powered right or is not soldered correctly on the PCB (cold solder). As you mentioned, since the emulator cannot communicate with the target, you won't see that much activity on the JTAG signals.

  • Thanks, this is actually my first board design so its helpful to be pointed in the right direction even though it was something as simple as this. It turned out there were actually both of these problems--there was a problem with VDDINT as well as an open caused by a bad solder connection.