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MPC5775K JTAG resets every 300ms?

Question asked by whoam on Oct 25, 2017
Latest reply on Oct 26, 2017 by whoam



I'm currently having a strange problem with the MPC5775K. 

I'm trying to create my own flash programming tool following AN4365 ( ) and this Example JTAG access – Addendum to application notes AN3283 and AN4365.

The external tool is another µC which is bit banging the JTAG messages over GPIO. I am able to enter Debug Mode, but every ~300ms there is an reset on TRST and the communication is also reseted, but I never pull the reset pin down except for the enter debug mode routine. So the MPC5775K must try to reset the JTAGC. When I'm using the Lauterbach Debugger it seems to work. I attached the screenshot from the JTAG communication to show the problem.

The first one is without anything connected, the second one with the lauterbach debugger and the last one with my external tool. In the first screenshot you can clearly see that the MPC5775K is causing the resets. In the last one you can see that the verifying of the Status Register works until the reset occurs. Can anyone explain me why this is happening and how I can solve the problem?


Thanks in advance and regards