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K64 Reset pin oscillating on Power up and will not allow Multilink Universal to Force a Flash
Allen S. Nov 10, 2015 at 04:21 PM (16:21 hours)
Staff: Takao Y.

  • I have created a custom target solution with a K64F512 series uP and have tried to get the debugger to work with my newly acquired Multilink Universal PEMicro Module.  I have a 10 pin JTAG interface on the custom board and have verified the wiring that goes between the Multilink and the custom board.  The Yellow LED on the Multilink turns on when power is applied to the target.  The Blue LED is on and I have no problems with the drivers when using KDS 3.0.  Even CW 10.6 sees the Multilink Universal module.  I have verified that the uP is starting correctly by watching the PU an PD on the respective pins for the JTAG interface.  The only thing that was puzzeling is the RESET_b pin was oscillating.  Further investigation has led me to the conclusion that this is normal and is occurring because the flash is blank and needs a dummy application flash in before the reset pin will function in a normal mode.  I have a couple of questions: 1. How can I force flash a dummy application into the blank flash because every time I try, the KDS 3.0 debugger using the PEMicro Multilink Interface Module says it can not connect to the target? 2. Is there a more direct way of using the Multilink Universal Interface module to diagnose and determine the cause of not being able to connect to the target uP?


  • Greetings,

    You are correct that if the flash is blank, then the watchdog is going to continually trigger when you power up the board. Not just a dummy application, but code that disables the watchdog will prevent the reset pin from toggling.

    If you use the P&E interface with KDS, you should attempt to flash program or debug and it will be able to get past this problem. Unless you disconnect the reset line. What would happen is the P&E interface would take control of the reset line by holding it down. This prevents any code from running and watchdog is not alive. Then on releasing the reset line, the proper input and output signals will allow it to enter debug mode.

    Note, the P&e interface needs to be able to control the RESET line. If your design has a system bus chip, external watchdog, or other circuitry on reset, it may affect the P&E tool from getting into debug mode.

    You can easily test this in KDS by creating a blank project for your chip and simply debug it.

    Takao Yamada

    • Hello Takao,

      No external watchdog. No system bus chip. Only have a 100K pullup on the reset_b pin. I did create a blank project and attempt to program it in debug mode and I get the P&E Connection Assistant showing USB Multilink - USB Port and UMultilink Universal Rev C on USB1 which gives me the choice to retry or abort.

      I am assuming that the reason I could not connect to the target was due to the reset line oscillating, but apparently that is not the case. At this point I am going to have to assume that there is a wiring issue between the Multilink Universal Interface to the target board or there may be some kind of a timing issue.

      No matter what I try, I keep getting the message Target not connected.

      As far as I can tell the wiring for the JTag Interface is pretty straight forward as I have made a cable that interface to the target board and the plug in connector that comes out of the Universal Multilink Module.

      Is there a limit to the length of cabling that JTAG does not support?

      Any other ideas?

  • On a side note: I am using Port B pins 1 through 10 on the Universal Multilink module.  I have these same pins mapped to the target board as well using a 10 pin header.

    • I figured it out.  I had the cable wired for a Port F configuration instead of a Port B configuration.  After making the necessary changes, the debugger was able to flash in the dummy project and all was happy.  Now for the real fun.

      Thanks for your help.

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