Atmel SAM4S Series, Preliminary Data Sheet

Page: 544 / 1163

544
11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
29.5.10 Input Edge/Level Interrupt
The PIO Controller can be programmed to generate an interrupt when it detects an edge or a
level on an I/O line. The Input Edge/Level Interrupt is controlled by writing PIO_IER (Interrupt
Enable Register) and PIO_IDR (Interrupt Disable Register), which respectively enable and dis-
able 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 succes-
sive 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, controlled by the PIO Controller or assigned to a peripheral function.
By default, the interrupt can be generated at any time an edge is detected on the input.
Some additional Interrupt modes can be enabled/disabled by writing in the PIO_AIMER (Addi-
tional Interrupt Modes Enable Register) and PIO_AIMDR (Additional Interrupt Modes Disable
Register). The current state of this selection can be read through the PIO_AIMMR (Additional
Interrupt Modes Mask Register)
These Additional Modes are:
• Rising Edge Detection
• Falling Edge Detection
• Low Level Detection
• High Level Detection
In order to select an Additional Interrupt Mode:
• The type of event detection (Edge or Level) must be selected by writing in the set of registers;
PIO_ESR (Edge Select Register) and PIO_LSR (Level Select Register) which enable
respectively, the Edge and Level Detection. The current status of this selection is accessible
through the PIO_ELSR (Edge/Level Status Register).
• The Polarity of the event detection (Rising/Falling Edge or High/Low Level) must be selected
by writing in the set of registers; PIO_FELLSR (Falling Edge /Low Level Select Register) and
PIO_REHLSR (Rising Edge/High Level Select Register) which allow to select Falling or
Rising Edge (if Edge is selected in the PIO_ELSR) Edge or High or Low Level Detection (if
Level is selected in the PIO_ELSR). The current status of this selection is accessible through
the PIO_FRLHSR (Fall/Rise - Low/High Status Register).
When an input Edge or Level is detected on an I/O line, the corresponding bit in PIO_ISR (Inter-
rupt 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 generate a single interrupt signal to the Nested Vector Interrupt Controller (NVIC).
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. When an Interrupt is
enabled on a “Level”, the interrupt is generated as long as the interrupt source is not cleared,
even if some read accesses in PIO_ISR are performed.