SAM7S128_14 Datasheet, PDF (246/775 Pages) ATMEL Corporation – ARM-based Flash MCU

Figure 27-5. Input Glitch Filter Timing
MCK
Pin Level
PIO_PDSR
if PIO_IFSR = 0
PIO_PDSR
if PIO_IFSR = 1
1 cycle 1 cycle
up to 1.5 cycles
1 cycle
2 cycles
up to 2.5 cycles
1 cycle
1 cycle
up to 2 cycles
27.4.10
Input Change Interrupt
The PIO Controller can be programmed to generate an interrupt when it detects an input change
on an I/O line. The Input Change Interrupt is controlled by writing PIO_IER (Interrupt Enable
Register) and PIO_IDR (Interrupt Disable Register), which respectively enable and disable the
input change interrupt by setting and clearing the corresponding bit in PIO_IMR (Interrupt Mask
Register). As Input change detection is possible only by comparing two successive samplings of
the input of the I/O line, the PIO Controller clock must be enabled. The Input Change Interrupt is
available, regardless of the configuration of the I/O line, i.e. configured as an input only, con-
trolled by the PIO Controller or assigned to a peripheral function.
When an input change is detected on an I/O line, the corresponding bit in PIO_ISR (Interrupt
Status Register) is set. If the corresponding bit in PIO_IMR is set, the PIO Controller interrupt
line is asserted. The interrupt signals of the thirty-two channels are ORed-wired together to gen-
erate a single interrupt signal to the Advanced Interrupt Controller.
When the software reads PIO_ISR, all the interrupts are automatically cleared. This signifies that
all the interrupts that are pending when PIO_ISR is read must be handled.
Figure 27-6. Input Change Interrupt Timings
MCK
Pin Level
PIO_ISR
Read PIO_ISR
APB Access
APB Access
27.5 I/O Lines Programming Example
The programing example as shown in Table 27-1 below is used to define the following
configuration.
• 4-bit output port on I/O lines 0 to 3, (should be written in a single write operation), open-drain,
with pull-up resistor
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
246