This register controls the GPIO pins.
|Bits[7:4]||Must be '0'|
|Bits[3:2]||GPIOC[2:1]: GPIO 1 and 2 control|
| These bits determine if the corresponding GPIOD pin is an input or output.
0 = Output
1 = Input (default)
|Bits[1:0]||GPIOD[2:1]: GPIO 1 and 2 data|
| These bits are used to read and write data to the GPIO ports.
When reading the register, the data returned correspond to the state of the GPIO external pins, whether they are programmed as inputs or as outputs. As outputs, a write to the GPIOD sets the output value. As inputs, a write to the GPIOD has no effect. GPIO is not available in certain respiration modes.