4.18.5.1 Pull-up and Purell-down Resistor Control

Each I/O line is designed with an embedded pull-up resistor and an embedded pull-down resistor. The pull-up resistor can be enabled or disabled by writing to the Pull-Up Enable register (PIO_PUER) or Pull-Up Disable register (PIO_PUDR), respectively. Writing to these registers results in setting or clearing the corresponding bit in the Pull-Up Status register (PIO_PUSR). Reading a one in PIO_PUSR means the pull-up is disabled and reading a zero means the pull-up is enabled. The pull-down resistor can be enabled or disabled by writing the Pull-Down Enable register (PIO_PPDER) or the Pull-Down Disable register (PIO_PPDDR), respectively. Writing in these registers results in setting or clearing the corresponding bit in the Pull-Down Status register (PIO_PPDSR). Reading a one in PIO_PPDSR means the pull-up is disabled and reading a zero means the pull-down is enabled.

Enabling the pull-down resistor while the pull-up resistor is still enabled is not possible. In this case, the write of PIO_PPDER for the relevant I/O line is discarded. Likewise, enabling the pull-up resistor while the pull-down resistor is still enabled is not possible. In this case, the write of PIO_PUER for the relevant I/O line is discarded.

Control of the pull-up resistor is possible regardless of the configuration of the I/O line.

After reset, depending on the I/O, pull-up or pull-down can be set.