Cirrus Logic CS5378 - Manual (Page 65)

CS5378
DS639F3 65
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 CS5378 attempts to drive
the pin high. If an external device forces the pin
low, the read value reflects the pin state and returns
a logical 0. Similarly, if an output pin is written as
a logical 0 but forced high externally, the read val-
ue reflects the pin state and returns a logical 1. In
both cases the CS5378 is in contention with the ex-
ternal device resulting in increased power con-
sumption.