Hi.
Using Tiva TM4C123GH6PM part on Tiva Launchpad Evaluation Kit EK-TM4C123GXL
1) Although there are volumes of documentation on the Tiva series parts, I have been unable to discover how I might, with certainty, tri-state a GPIO when set as output.
Would using the DEN register achieve this?
2) Is there any documentation that gives an indication of the nature of the gpio pin's electronic circuitry?
2a) In particular, is the output normally configured as a totem pole unless the open drain is enabled? Or something else?
2b) What are the equivalent series resistances to Vdd and Gnd when the output pin is HIGH and LOW respectively (and not configured as open drain)? Testing indicates that the equivalent resistance to ground might be in the region of 29 Ohms when low and around 33 Ohms to Vdd when high. Would these values be correct? Is there much variance from port to port (pin to pin) and across parts?
2c) What might be the effective capacitance on the pin when configured as an input? Likewise with the variance question of 2b.
I hope I have not missed details of all these matters somewhere in the documentation.
Thank you for considering these questions.
Take care.
Mike