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TM4C1292NCPDT: TM4C1292NCPDTI3 Part Variant - Change to I2C1SCL pin 49 Idle State?

Timothy Waryas
Prodigy 10 points
Part Number: TM4C1292NCPDT

Hello,

I have two microcontroller PCBs where TM4C1292NCPDTT3 and TM4C1292NCPDTI3 are used as part variants

I cannot find anywhere in the datasheet what the functional difference is in the TM4C1292NCPDTI3 variant.

I am having trouble with microcode halting on my TM4C1292NCPDTI3 board, and I have measured that the inactive state for the I2C1SCL pin 49 clock line is 0V instead of 3.3V like it is on the TM4C1292NCPDTT3 board. Scope captures below.

TM4C1292NCPDTI3 

TM4C1292NCPDTT3

Is this normal behavior for the TM4C1292NCPDTI3 and is TM4C1292NCPDTT3 inverted?

Best,

Tim

  • 0
    Prodigy 10 points

    Sorry the image links were copied above, here is the one for TM4C1292NCPDTI3 

  • 0 in reply to Timothy Waryas
    TI__Guru**** 182576 points

    Hi,

      The only difference between the two part numbers is the temp rating. 

    Timothy Waryas said:

    I am having trouble with microcode halting on my TM4C1292NCPDTI3 board, and I have measured that the inactive state for the I2C1SCL pin 49 clock line is 0V instead of 3.3V like it is on the TM4C1292NCPDTT3 board. Scope captures below.

    As mentioned, these two parts are identical except the temp rating. I highly suspect that your second board does not have a proper pullup. you must have a external pullup resistor. Please check if a pullup is in place on that board. If the pullup is there then check for proper soldering or replace the pullup with a new one and see if the problem is still there. The MCU does not hold the SCL and SDA high during idle. That is to be handled by the external pullup resistor.