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TM4C129ENCPDT: Crystal vs PIOSC during programming

Darren Jenkins
Genius 12461 points
Part Number: TM4C129ENCPDT

TM4C team,

Our customer is having some problems accessing the TM4C129 memory during programming over JTAG.  The board has a crystal on it that normally is used to drive the System clock in their application.  I know the TM4C129 also has the internal oscillator PIOSC.  There is a concern about whether the external crystal (or the associated pins) could be related to the problem during JTAG programming.

Can you confirm that during JTAG programming, the TM4C will not use the external crystal oscillator?  

Does it rely on PIOSC or something else?

Thanks,

Darren

  • 0
    TI__Guru**** 191146 points

    Hi Darren,

    Darren Jenkins said:
    There is a concern about whether the external crystal (or the associated pins) could be related to the problem during JTAG programming.

    Is the customer using the Ethernet? If not, a RBIAS connection to the GND is still required. Please see below errata and see if the problem the customer is facing relevant to this one. 

     

    Darren Jenkins said:

    Can you confirm that during JTAG programming, the TM4C will not use the external crystal oscillator?  

    Does it rely on PIOSC or something else?

    The JTAG programmer will scan the flash programmer code to the SRAM and the processor will run the programmer code out of the SRAM to download the firmware image. The programming is done on the SYSCLK. If the MOSC was the source of the SYSCLK then you can say the SYSCLK is dependent on the MOSC. 

    There is this note in the datasheet that needs to be obeyed.