SAM4L Datasheet, PDF (841/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

31.4 I/O Lines Description
Table 31-1. I/O Lines Description
Pin Name
Pin Description
PAD_EVT[n] External Event Inputs
Type
Input
ATSAM4L4/L2
31.5 Product Dependencies
In order to use this module, other parts of the system must be configured correctly, as described
below.
31.5.1 I/O Lines
Multiplexed I/O lines can be used as event generators. To generate a peripheral event from an
external source the source pin must be configured as an input pin by the I/O Controller. It is also
possible to trigger a peripheral event by driving these pins from registers in the I/O Controller, or
another peripheral output connected to the same pin.
31.5.2
Power Management and Low Power Operation
As the peripheral events do not require CPU intervention, they are available in Idle mode. They
are also available in deeper Power Save Modes if both the generator and user remain clocked in
that mode.
In deeper Power Save Modes, certain events can be issued even when the system clock is
stopped, and revive unclocked user peripherals. The clock will be restarted for this module only,
without waking the system from Power Save Mode. The clock remains active only as long as
required by the triggered function, before being switched off again, and the system remains in
the original sleep mode. The CPU and system will only be woken up if the user peripheral gener-
ates an interrupt as a result of the operation. This concept is known as SleepWalking^™ and is
described in further detail in Section 10. ”Power Manager (PM)” on page 102. Note that asyn-
chronous peripheral events may be associated with a delay due to the need to restart the
system clock source if this has been stopped in the sleep mode.
Refer to the Module Configuration section at the end of this chapter for the device-specific con-
figuration, especially on which peripheral event generators and users can rely on
SleepWalking™.
The table and diagram below represent the timed behavior of SleepWalking™ operations:
Table 31-2.
Phase
1
2
3
4
SleepWalking™ on Peripheral Events
Operation
while in a Power Save Mode where peripheral clocks are asleep,
asynchronous Generator j sends Peripheral Event to PEVC
incoming Event is detected by EVS j , and CLK_PEVC requested to PM
upon reception of clock request, PM wakes clock sources if required
CLK_PEVC wakes up
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