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AM2634: WARM Reset output

Jeeuk Chang
Prodigy 145 points
Part Number: AM2634
Other Parts Discussed in Thread: TPS22918

Tool/software:

Hi, TI expert.

I made AM2634 test board and put the "WARMRSTn" pin floating.

When I powered my AM2634 test board, I watched only low signal on "WARMRSTn" pin.

When I added 10k-Ohm pull-up resistor, I found high signal with 3 ms delay after PORz signal.

1. In AM2634 datasheet, the pin type of "WARMRSTn" is "IO".

Is the method using pull-up resistor right?

2. It seems that I can set internal pull-up resistor for "WARMRSTn" via "MSS_IOMUX_WARMRSTN_CFG_REG".

But I can not find APIs dealing the registers.

I found "soc_rcm.h" and "soc_rcm.c" but they does not control "MSS_IOMUX_WARMRSTN_CFG_REG".

  • 0
    TI__Expert 4486 points

    Hi Jeeuk Chang,

    Jeeuk Chang said:

    In AM2634 datasheet, the pin type of "WARMRSTn" is "IO".

    Is the method using pull-up resistor right?

    As mentioned in the datasheet, Warm Reset pin can be both Warm Reset Request (Input) and Warm Reset Status (Output). The Warm Reset Status output is pulled high after POR is de-asserted and a certain delay, as shown in the below picture from datasheet and hence a pull-up resistor is not required.

    Jeeuk Chang said:

    It seems that I can set internal pull-up resistor for "WARMRSTn" via "MSS_IOMUX_WARMRSTN_CFG_REG".

    But I can not find APIs dealing the registers.

    I found "soc_rcm.h" and "soc_rcm.c" but they does not control "MSS_IOMUX_WARMRSTN_CFG_REG".

    You can configure that using the file \source\drivers\pinmux\am263x\pinmux.c

  • 0 in reply to Sahana H G
    Prodigy 145 points

    Hi, TI expert.

    I could change IOMUX settings of WARMRSTN pin using "pinmux.c"

    But, without external pull-up resistor on "WARMRSTn" pin, its output is always zeros.

    With external pull-up resistor on "WARMRSTn" pin, its output is high after PORz with a delay.

    -

    This table is my result.

    I changed the values of IOMUX_WARMSTN_CFG_REG at CCS.

    The output pin of WARMRSTn is connected to TPS22918 load switch input.

    -

    From my result, I concluded ...

    1. WARMRSTn is open drain output.

    2. Internal pull-up resistor for WARMRSTn does not operate.

    3. Internal pull-down resistor for WARMRSTn is 20 kΩ and can be used.

    4. Output override "0" for WARMRSTn can be used.

  • 0 in reply to Jeeuk Chang
    TI__Expert 4486 points

    Hello,

    Apologies, I missed that WARMRSTn is Open Drain pin. You're right, we would need an external Pull-up of 10kohm as present in the EVM schematics.

    Hope your query is solved.

    Regards,

    Sahana