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TM4C129 PWM Pin Locations

Adam Mixter
Intellectual 320 points
Other Parts Discussed in Thread: EK-TM4C1294XL

Hello All,

I was reviewing the literature for both the TM4C129X Evaluation kit and the TM4C129NCPDT Microcontroller. Between the two I am seeing a difference in which pins are are set for PWM use. 

The Table from the MCU guide:

The tables from the EK guide.

As you may note The EK lists more availible PWM signals than the MCU. Pin PF0 Specifically is listed as a PWM output in MCU and not listed as such in the EK guide. What should I believe?

Regards.

Adam

  • 0
    Guru 47900 points

    Might it be that, "Not all" PWM pins w/in the MCU are "brought out" to the EK board's headers? Such is not unusual - and occurs across most all ARM MCU vendors' Eval boards...

    On a "re-read" of your post - I (now) note that the "mystery pins" are: PM0 & PM3.   Neither appear w/in your MCU PWM listing.

    As a guess - those 2 PM pins (0 & 3) are at "risk" and may be best to avoid.   (at least for their "questionable" PWM usage.)

    You're still left w/7 serviceable PWM pins (indeed PF0 is awol from the headers) & 6 PWM pins proves, "Good for (most) Gov't Work!"

    It's possible that the EK board employs other than the 128 pin QFP device your top chart specifies...

  • 0
    TI__Guru**** 244400 points
    Hello Adam,

    If you check there are 2 aspects to the table from the boosterpack header. Even if the function is mentioned as PWM it does not mean that a PWM generator needs to be there. A timer CCP pin can also work as PWM with control from the timer module and in this case the PWM is coming from Timer and not PWM

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 47900 points

    Hi Amit,

    I've a different take - 7 of the normal/customary PWM Module type pins "survive & propagate" to board headers!   Only PF0 missed that ideal.

    Real conflict remains (as earlier stated) PM0 & PM3.   (are those PWM module pins - or (just) Timer pins - perhaps as you indicate?)

    I don't believe that Timers - pressed into service as (lesser) PWM - is indicated in these charts!

  • 0 in reply to Amit Ashara
    Intellectual 320 points
    Hello Amit,

    Is there any reason to believe that PF0 would be more difficult to set up, than for example PF1?
  • 0 in reply to cb1
    TI__Guru**** 244400 points
    Hello cb1,

    Yes, that is correct, 7 pins do come out. But there are 2 pins PM0 and PM7 that are in fact T5CCP1 and T2CCP0 but indicated as PWM function. PF0 is for LED D4 on the EK-TM4C1294XL.

    Regards
    Amit
  • 0 in reply to Adam Mixter
    TI__Guru**** 244400 points
    Hello Adam,

    Yes, PF0 is a locked pin and requires Unlock-Commit-Lock to be performed for proper configuration and is arguably one that has been heavily debated on the forum.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Guru 47900 points

    Hi Amit,

    Does PF0 continue its, "Death march" (pardon, I meant hallowed, much demanded, NMI default status) w/in newer 129x series? (I thought not...)

    There is NO debate - forcing TWO pins into unwanted NMI default status cannot be justified - and torments users (we suspect) forever!

  • 0 in reply to cb1
    Intellectual 320 points
    Hello Amit,

    I am pretty certain that in order to unlock, commit and re-lock the pin in question there would be some trade off. What Might that trade off be?

    I also see I have a Pin (PM7) I was planning to use as analog input instead of a pwm. Would the process to alter this pin be similar to the PF0 case?
  • 0 in reply to Adam Mixter
    TI__Guru**** 244400 points
    Hello Adam,

    The tradeoff would be the additional instruction time to program the pin. 6 pins on the device have the requirement for Unlock, commit and relock. These are 2 NMI pins and 4 JTAG pins. No other pins require this overhead

    Regards
    Amit