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WAKE pin ground recommended?

Richard Bland
Expert 2050 points

TM4C123

the data sheet suggests on (p1401 table 23-7) that the !WAKE pin should be wired low if you don't want an external wake-up function

however I find that on power up the !HIB pin is lo indicating that the processor is in HIB mode - if I put a pull up on !WAKE pin (as on Launchpad) then the !HIB pin is hi after power up indicating the processor is awake

also I have connected the 4 JTAG wires from an ICD1 to my processor, there is a 25MHz clock running and all power seems good, but LMFlash programmer says "Error unable to initialise target - 0" : any ideas what I've done wrong?

Thanks

Richard

  • 0
    TI__Expert 3555 points

    Hi Richard,

    Is this your own custom board or is this a LaunchPad or DK from TI you are using?

    If unused, the WAKE# pin is recommended to be grounded as a general good practice for low noise.  Having WAKE# tied low will not cause the TM4C123 to enter hibernate.  It is only used as a wake indicator and would need to be enabled as such prior to entering hibernate. 

    Do you have the 32Khz crystal or oscillator source connected?  This needs to be present on the TM4C123 for the hibernation module to function, including the HIB pin state. 

    For the JTAG you have the 4 wires of the ICDI connected.  Which ICDI are you using.  Do you also have GND connected?

    You indicate there is a 25Mhz clock running.  What is the source of your 25Mhz clock?

    -Ken

  • 0 in reply to Stellaris Ken
    Expert 2050 points

    Hi Ken,

    Thanks for your time here - yes it is our own board - very embarassing - I just spotted we have the main 25MHz oscillator connected to XOSC instead of OSC0. Having rectified that error and put the !WAKE pin back to ground and tied XOSC to ground too, all is working fine and the ICD1 connects and I can debug :)

    Oh well, it's what a prototype board is for I suppose - Sorry!

    regards

    Richard