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Which GPIOs on OMAP L138 support Open Drain operation?

Soren Steen Christensen
Genius 3685 points

Other Parts Discussed in Thread: OMAP-L138, OMAP-L137

Hi Support,

On the Hawkboard mailinglist we have just had a discussion about which GPIOs on OMAP-L138 support Open Drain operation? From the Data Manual this isn't 100% clear (at least not to me). From the last bullet of section 6.31 at page 247 in http://focus.ti.com/lit/ds/symlink/omap-l138.pdf you get the impression that all GPIOs support Open Drain operation, but to be honest I find this very hard to believe? :-)

Main reason for not believing this is, that I wouldn't expect balls like LCD_Dx-, EMA_Ax and EMA_CSx (which as well can be used a GPIOs) to be driven by Open Drain output cells?

Comparing to http://focus.ti.com/lit/ds/symlink/omap3530.pdf the OMAP-L138 data manual is missing a cell-type description for each ball giving the actual cell type of "LVCMOS/Open Drain/subLVDS/etc". Where does similar information exist for OMAP-L137/L138/AM17xx/etc?

Hoping that somebody can put some light on this?

Best regards and thanks in advance
  Søren

  • 0
    TI__Expert 3540 points

    The only open-drain IOs are the I2C signals and they are open-drain ONLY when configured as I2C functions. Otherwise, they are normal totem-pole CMOS outputs.

    Regards,

    Clay

  • 0 in reply to Clay Turner
    Genius 3685 points

    Hi Clay,

    Thanks for quick support. I would strongly recommend to add this information to the Data Manual as well. Currently it's from the GPIO chapter kind of easy to get the impression that all pins support OD operation in case you aren't knowledge about chip-internal-design-principles...

    Best regards and thanks for clarifying - I will forward the information to the HawkBoard list...
      Søren

  • 0 in reply to Clay Turner
    Intellectual 510 points

    According to the datasheet (sprs586d.pdf) the /RESETOUT function has also open drain capabilities - is this correct ? So is it the I2C and /RESETOUT that are open drain (when configured as output ?).

    I would second Soren that this should be clarified in the data sheet for each ball (or is it, I haven't found it yet).

    All the best,.

    Boris.