Further on Ixp432 debugging

Development Boards MicroMod
1

I have just down load the latest OpenOCD version (546) and found

it working much better and faster than the previous version I was using.

Thanks for the hard work.

I have been struggling with reliability problems for the last 4 months, and finally cured it yesterday.

The solution was to add a 100pF capacitor to the TCK line at the connector

where the signal came on to the board. The signal was being driven by an Amontec JTAG Key.

I had looked at these signals on many occasions without success and as they looked clean I had not though anything was needed, and actually was blaming the software (Sorry).

I looked again yesterday as a new board was giving me a lot of grief. I used an old scope with larger capacitive load and the problem went away just like that.

I do not have any similar problems with other chips I debug and can only assume that the silicon process used for the ixp432 is much faster that most and it was capable of seeing very small glitches caused by noise.

I have now been running the board for 2 days without problems, and it feels great.

Any way I hope this note may help other people.

Dave

PS

The TCK signal also passes through a 100R series resistor, then to the 100pF capacitor.

2

Hi,

Thank you for your advice concerning your IxP432 and your Amontec JTAGkey.

Also, RC (100R + 100pF) filter could help the stability of the JTAG chain.

The RC should be placed as close as possible to the on-board device.

In an other hand, this could means you have noise on your board, and I could advice you check the power and EMI of your board before production!!! check you decoupling capacitiors too!!!

Also, check the TDO and TCK line. They should not be routed parallel on your board, or if this is the case, place a GND wire between the TDO and TCK (shielding TCK).

We have seen on some customer boards that the TCK could affect TDO signal by line capacitance.

  • Laurent

http://www.amontec.com