Cirrus Logic CS5376A - Manual (Page 69)

CS5376A
DS612F4 69
Any GPIO pin can be used as an open-drain output
by setting the data value to 0, enabling the pull-up,
and using the GP_DIR direction bits to control the
pin value. This open-drain output configuration
uses the internal pull-up resistor to hold the pin
high when GP_DIR is set as an input, and drives the
pin low when GP_DIR is set as an output.
19.5.1 GPIO Reads in Output Mode
When reading GPIO pins the GP_DATA register
value always reports the current state of the pins, so
a value written in output mode does not necessarily
read back the same value. If a pin in output mode is
written as a logical 1, the CS5376A attempts to
drive the pin high. If an external device forces the
pin low, the read value reflects the pin state and re-
turns a logical 0. Similarly, if an output pin is writ-
ten as a logical 0 but forced high externally, the
read value reflects the pin state and returns a logical
1. In both cases the CS5376A is in contention with
the external device resulting in increased power
consumption.