33.5.6 Open Drain Mode

Each I/O can be independently programmed in Open Drain mode. This feature permits several drivers to be connected on the I/O line which is driven low only by each device. An external pull-up resistor (or enabling of the internal one) is generally required to ensure a high level on the line.

Open Drain mode is controlled by the (S_)PIO_CFGRx.OPD bit. The mode can be selected if the I/O line is not controlled by a peripheral. (S_)PIO_CFGRx.FUNC must be cleared.

For more details about Open Drain mode, see PIO_CFGRx, or S_PIO_CFGRx for a secure I/O line configuration.

After reset, the OPD bit for each I/O line is defined at the product level and depends on the device multiplexing.

Note: The Open Drain feature cannot be used when the I/O line is driven by a peripheral. Only software control (GPIO mode) can manage the open drain for an I/O line. TWI is able to manage open drain because this peripheral does not require the PIO to be configured in Open Drain mode.