Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

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SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]

11063K–ATARM–05-Nov-13

When the I/O line is assigned to a peripheral function, i.e., the corresponding bit in PIO_PSR is at zero, the drive of the
I/O line is controlled by the peripheral. Peripheral A or B or C or D depending on the value in PIO_ABCDSR1 and
PIO_ABCDSR2 determines whether the pin is driven or not. 

When the I/O line is controlled by the PIO Controller, the pin can be configured to be driven. This is done by writing the
Output Enable register (PIO_OER) and Output Disable register (PIO_ODR). The results of these write operations are
detected in the Output Status register (PIO_OSR). When a bit in this register is at zero, the corresponding I/O line is used
as an input only. When the bit is at one, the corresponding I/O line is driven by the PIO Controller.

The level driven on an I/O line can be determined by writing in the Set Output Data register (PIO_SODR) and the Clear
Output Data register (PIO_CODR). These write operations, respectively, set and clear the Output Data Status register
(PIO_ODSR), which represents the data driven on the I/O lines. Writing in PIO_OER and PIO_ODR manages PIO_OSR
whether the pin is configured to be controlled by the PIO Controller or assigned to a peripheral function. This enables
configuration of the I/O line prior to setting it to be managed by the PIO Controller. 

Similarly, writing in PIO_SODR and PIO_CODR affects PIO_ODSR. This is important as it defines the first level driven
on the I/O line.

Clearing one or more PIO line(s) and setting another one or more PIO line(s) synchronously cannot be done by using
PIO_SODR and PIO_CODR registers. It requires two successive write operations into two different registers. To
overcome this, the PIO Controller offers a direct control of PIO outputs by single write access to PIO_ODSR. Only bits
unmasked by the Output Write Status register (PIO_OWSR) are written. The mask bits in PIO_OWSR are set by writing
to the Output Write Enable register (PIO_OWER) and cleared by writing to the Output Write Disable register
(PIO_OWDR).

After reset, the synchronous data output is disabled on all the I/O lines as PIO_OWSR resets at 0x0.

Each I/O can be independently programmed in open drain by using the multi-drive feature. 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 guarantee a high level on the line.

The multi-drive feature is controlled by the Multi-driver Enable register (PIO_MDER) and the Multi-driver Disable register
(PIO_MDDR). The multi-drive can be selected whether the I/O line is controlled by the PIO Controller or assigned to a
peripheral function. The Multi-driver Status register (PIO_MDSR) indicates the pins that are configured to support
external drivers.

After reset, the multi-drive feature is disabled on all pins, i.e. PIO_MDSR resets at value 0x0.

 shows how the outputs are driven either by writing PIO_SODR or PIO_CODR, or by directly writing

PIO_ODSR. This last case is valid only if the corresponding bit in PIO_OWSR is set. 

 also shows when the

feedback in the Pin Data Status register (PIO_PDSR) is available.