Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet
Product codes
AT91SAM9N12-EK
216
SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]
11063K–ATARM–05-Nov-13
Figure 23-4. Output Line Timings
23.5.8 Inputs
The level on each I/O line can be read through PIO_PDSR. This register indicates the level of the I/O lines regardless of
their configuration, whether uniquely as an input, or driven by the PIO Controller, or driven by a peripheral.
their configuration, whether uniquely as an input, or driven by the PIO Controller, or driven by a peripheral.
Reading the I/O line levels requires the clock of the PIO Controller to be enabled, otherwise PIO_PDSR reads the levels
present on the I/O line at the time the clock was disabled.
present on the I/O line at the time the clock was disabled.
23.5.9 Input Glitch and Debouncing Filters
Optional input glitch and debouncing filters are independently programmable on each I/O line.
The glitch filter can filter a glitch with a duration of less than 1/2 master clock (MCK) and the debouncing filter can filter a
pulse of less than 1/2 period of a programmable divided slow clock.
pulse of less than 1/2 period of a programmable divided slow clock.
The selection between glitch filtering or debounce filtering is done by writing in the PIO Input Filter Slow Clock Disable
register (PIO_IFSCDR) and the PIO Input Filter Slow Clock Enable register (PIO_IFSCER). Writing PIO_IFSCDR and
PIO_IFSCER, respectively, sets and clears bits in the Input Filter Slow Clock Status register (PIO_IFSCSR).
register (PIO_IFSCDR) and the PIO Input Filter Slow Clock Enable register (PIO_IFSCER). Writing PIO_IFSCDR and
PIO_IFSCER, respectively, sets and clears bits in the Input Filter Slow Clock Status register (PIO_IFSCSR).
The current selection status can be checked by reading the register PIO_IFSCSR.
If PIO_IFSCSR[i] = 0: The glitch filter can filter a glitch with a duration of less than 1/2 master clock period.
If PIO_IFSCSR[i] = 1: The debouncing filter can filter a pulse with a duration of less than 1/2 programmable divided
slow clock period.
slow clock period.
For the debouncing filter, the period of the divided slow clock is performed by writing in the DIV field of the Slow Clock
Divider register (PIO_SCDR.
Divider register (PIO_SCDR.
Tdiv_slclk = ((DIV+1)*2).Tslow_clock
When the glitch or debouncing filter is enabled, a glitch or pulse with a duration of less than 1/2 selected clock cycle
(selected clock represents MCK or divided slow clock depending on PIO_IFSCDR and PIO_IFSCER programming) is
automatically rejected, while a pulse with a duration of one selected clock (MCK or divided slow clock) cycle or more is
accepted. For pulse durations between 1/2 selected clock cycle and one selected clock cycle, the pulse may or may not
be taken into account, depending on the precise timing of its occurrence. Thus for a pulse to be visible, it must exceed
one selected clock cycle, whereas for a glitch to be reliably filtered out, its duration must not exceed 1/2 selected clock
cycle.
(selected clock represents MCK or divided slow clock depending on PIO_IFSCDR and PIO_IFSCER programming) is
automatically rejected, while a pulse with a duration of one selected clock (MCK or divided slow clock) cycle or more is
accepted. For pulse durations between 1/2 selected clock cycle and one selected clock cycle, the pulse may or may not
be taken into account, depending on the precise timing of its occurrence. Thus for a pulse to be visible, it must exceed
one selected clock cycle, whereas for a glitch to be reliably filtered out, its duration must not exceed 1/2 selected clock
cycle.
The filters also introduce some latencies, illustrated in
The glitch filters are controlled by the Input Filter Enable register (PIO_IFER), the Input Filter Disable register (PIO_IFDR)
and the Input Filter Status register (PIO_IFSR). Writing PIO_IFER and PIO_IFDR respectively sets and clears bits in
PIO_IFSR. This last register enables the glitch filter on the I/O lines.
and the Input Filter Status register (PIO_IFSR). Writing PIO_IFER and PIO_IFDR respectively sets and clears bits in
PIO_IFSR. This last register enables the glitch filter on the I/O lines.
When the glitch and/or debouncing filter is enabled, it does not modify the behavior of the inputs on the peripherals. It
acts only on the value read in PIO_PDSR and on the input change interrupt detection. The glitch and debouncing filters
require that the PIO Controller clock is enabled.
acts only on the value read in PIO_PDSR and on the input change interrupt detection. The glitch and debouncing filters
require that the PIO Controller clock is enabled.
2 cycles
APB Access
2 cycles
APB Access
MCK
Write PIO_SODR
Write PIO_ODSR at 1
PIO_ODSR
PIO_PDSR
Write PIO_CODR
Write PIO_ODSR at 0