Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet
Product codes
AT91SAM9N12-EK
214
SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]
11063K–ATARM–05-Nov-13
23.5.1 Pull-up and Pull-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.
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.
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, all of the pull-ups are enabled, i.e. PIO_PUSR resets at the value 0x0, and all the pull-downs are disabled,
i.e. PIO_PPDSR resets at the value 0xFFFFFFFF.
i.e. PIO_PPDSR resets at the value 0xFFFFFFFF.
23.5.2 I/O Line or Peripheral Function Selection
When a pin is multiplexed with one or two peripheral functions, the selection is controlled with the Enable register
(PIO_PER) and the Disable register (PIO_PDR). The Status register (PIO_PSR) is the result of the set and clear
registers and indicates whether the pin is controlled by the corresponding peripheral or by the PIO Controller. A value of
zero indicates that the pin is controlled by the corresponding on-chip peripheral selected in the ABCD Select registers
(PIO_ABCDSR1 and PIO_ABCDSR2). A value of one indicates the pin is controlled by the PIO Controller.
(PIO_PER) and the Disable register (PIO_PDR). The Status register (PIO_PSR) is the result of the set and clear
registers and indicates whether the pin is controlled by the corresponding peripheral or by the PIO Controller. A value of
zero indicates that the pin is controlled by the corresponding on-chip peripheral selected in the ABCD Select registers
(PIO_ABCDSR1 and PIO_ABCDSR2). A value of one indicates the pin is controlled by the PIO Controller.
If a pin is used as a general-purpose I/O line (not multiplexed with an on-chip peripheral), PIO_PER and PIO_PDR have
no effect and PIO_PSR returns a one for the corresponding bit.
no effect and PIO_PSR returns a one for the corresponding bit.
After reset, the I/O lines are controlled by the PIO Controller, i.e. PIO_PSR resets at one. However, in some events, it is
important that PIO lines are controlled by the peripheral (as in the case of memory chip select lines that must be driven
inactive after reset, or for address lines that must be driven low for booting out of an external memory). Thus, the reset
value of PIO_PSR is defined at the product level and depends on the multiplexing of the device.
important that PIO lines are controlled by the peripheral (as in the case of memory chip select lines that must be driven
inactive after reset, or for address lines that must be driven low for booting out of an external memory). Thus, the reset
value of PIO_PSR is defined at the product level and depends on the multiplexing of the device.
23.5.3 Peripheral
A
or
B or C or D Selection
The PIO Controller provides multiplexing of up to four peripheral functions on a single pin. The selection is performed by
writing PIO_ABCDSR1 and PIO_ABCDSR2.
writing PIO_ABCDSR1 and PIO_ABCDSR2.
For each pin:
The corresponding bit at level zero in PIO_ABCDSR1 and the corresponding bit at level zero in PIO_ABCDSR2
means peripheral A is selected.
means peripheral A is selected.
The corresponding bit at level one in PIO_ABCDSR1 and the corresponding bit at level zero in PIO_ABCDSR2
means peripheral B is selected.
means peripheral B is selected.
The corresponding bit at level zero in PIO_ABCDSR1 and the corresponding bit at level one in PIO_ABCDSR2
means peripheral C is selected.
means peripheral C is selected.
The corresponding bit at level one in PIO_ABCDSR1 and the corresponding bit at level zero in PIO_ABCDSR2
means peripheral D is selected.
means peripheral D is selected.
Note that multiplexing of peripheral lines A, B, C and D only affects the output line. The peripheral input lines are always
connected to the pin input.
connected to the pin input.
Writing in PIO_ABCDSR1 and PIO_ABCDSR2 manages the multiplexing regardless of the configuration of the pin.
However, assignment of a pin to a peripheral function requires a write in PIO_ABCDSR1 and PIO_ABCDSR2 in addition
to a write in PIO_PDR.
However, assignment of a pin to a peripheral function requires a write in PIO_ABCDSR1 and PIO_ABCDSR2 in addition
to a write in PIO_PDR.
After reset, PIO_ABCDSR1 and PIO_ABCDSR2 are zero, thus indicating that all the PIO lines are configured on
peripheral A. However, peripheral A generally does not drive the pin as the PIO Controller resets in I/O line mode.
peripheral A. However, peripheral A generally does not drive the pin as the PIO Controller resets in I/O line mode.