Follow up question I saw in the datasheet that most of the pins are high Z with pull down and some are for external peripherals just like the hardware engineer described. However, the datasheet did show that some – not a lot - are high Z with a pull up. Is the datasheet incorrect about those? For example, uart2_rts, pin AB25 on the CBB package.
Original question
1) If an OMAP pin is configured as a high impedance with either a pull up/down during power up and reset I can take advantage of that pull up/down to hold the line in a known state before the pin can be configured as an output. Therefore, I don’t need external pull ups/downs on the enable lines of external parts that would be driven by the OMAP once it is configured. Correct?
2) Once the OMAP is operating I can configure a pin as an input with the internal pull up active and use an open collector driver external to the OMAP to drive that input. Again, I wouldn’t need an external pull up. Correct?
TI Reply
On power on reset, most pins (not all) default state are High Z and internal pull down enabled. Internal Pulls ups are disabled. You should refer to the datasheet. Some pin states are configured by the Boot ROM for memory and peripheral booting. If a specific pin needs to be high, that conflicts with a internal pull down, it can be externally pulled high by a 10K ohm.
Open collector rise time maybe too slow for some application if internal pull up is used. Provision should be made just in case. Refer to datasheet for pull up drive strength of the pin being used.
