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Debugger issue due to possible pin noise

Other Parts Discussed in Thread: MSP430F5341

One of my designs uses the msp430f5341 using the Spi by Wire debugging interface and I'm encountering an odd problem I'm having trouble figuring out. My code is toggling a pin from high to low then back to high. When debugging, CCS5 will stop responding and I will get a "Problem halting cpu" error as soon as I step into the instruction that sets the pin to low.

I suspected that it may have something to do with a pullup resistor (sinking too much current) or noise getting transferred into the SBW lines. I checked the continuity in the circuit and did not notice anything wrong.

When I put a probe (1MOhm|10pF) on the line I am toggling, the debugging interface works fine. Another interesting thing is that when I put a probe on the SBWTCK line while debugging it works as well.

My programming circuit looks just like the one in figure 7 from:

I've seen no problems with programming or debugging so far, other than this one. 

If anyone has any thoughts, I would appreciate some input.



  • I have some questions and a suggestion.

    First the questions: What hardware do you use for SBW? Is a F16xx used on the “tool” side? Are the GPIO pins of that chip directly connected to your F5341 “target” without buffers? How are they connected? (PCB? Cable? Length?)

    Now the suggestion: MSP430 output pins are driven high/low and do not need pull-up/down resisters. I suggest that you do not add external resister and do not enable internal resister.  

  • I am not sure how to answer your first question, but my setup consists of:

    an MSP-FET430UIF connected to a simple board through ribbon cable that that sets up the programming circuit just like in Figure 7 from the link I posted. I initially made a mistake and shorted Pin 1 to Pin 11 on the JTAG connector (shorting RST/NMI to TDO). This allowed me to program and debug correctly until I encountered the problem. your question prompted me to verify my circuit and I realized that without shorting TDO and RST/NMI, the debugger does not work. I don't know why this is. The simple board is then connected through another ribbon cable to my actual board with the msp on it. The PCB contains the 2.2nF and 47kOhm pullup resistor from figure 7 of the link I posted earlier.

    I understand about the output pins on the MSP, but this particular pin that I am trying to toggle is the reset pin of another chip that needs to be held high even if the MSP is not flashed.

    Thanks for your help.

  • By the way. The pin I am trying to toggle is P1.7

  • I figured it out. I think another attachment board (the one supplying power and that programs the other chip) was browning out when that pin was toggled. Sourcing power from the MSP programmer seems to have fixed all the issues.