Data Sheet

408
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
23.5.5 Interrupts
The interrupt request line is connected to the interrupt controller. Using the EVSYS interrupts requires the interrupt
controller to be configured first. Refer to “Nested Vector Interrupt Controller” on page 34 for details.
23.5.6 Events
Not applicable.
23.5.7 Debug Operation
When the CPU is halted in debug mode, the EVSYS continues normal operation. If the EVSYS is configured in a way
that requires it to be periodically serviced by the CPU through interrupts or similar, improper operation or data loss may
result during debugging.
23.5.8 Register Access Protection
All registers with write-access are optionally write-protected by the Peripheral Access Controller (PAC), except the
following register:
z Interrupt Flag Status and Clear register (INTFLAG)
Write-protection is denoted by the Write-Protected property in the register description.
Write-protection does not apply for accesses through an external debugger. Refer to “PAC – Peripheral Access
Controller” on page 41 for details.
23.5.9 Analog Connections
Not applicable.
23.6 Functional Description
23.6.1 Principle of Operation
The EVSYS allows for communication between peripherals via events. Peripherals that respond to events (event users)
are connected to multiplexers which have all event channels as input. Each each event channel can be configured to
route signals from any peripheral emitting events (event generator) to one or more event users.
23.6.2 Basic Operation
23.6.2.1 Initialization
The peripheral that is to act as event generator must be configured to be able to generate events. The peripheral to act
as event user must be configured to handle incoming events.
When this has been done, the event system is ready to be configured. The configuration must follow this order:
1. Configure the event user by performing a single 16-bit write to the User Multiplexer register (USER) with:
1.1. The channel to be connected to a user is written to the Channel bit group (USER.CHANNEL)
1.2. The user to connect the channel is written to the User bit group (USER.USER)
2. Configure the channel by performing a single 32-bit write to the Channel (CHANNEL) register with:
2.1. The channel to be configured is written to the Channel Selection bit group (CHANNEL.CHANNEL)
2.2. The path to be used is written to the Path Selection bit group (CHANNEL.PATH)
2.3. The type of edge detection to use on the channel is written to the Edge Selection bit group
(CHANNEL.EDGSEL)
2.4. The event generator to be used is written to the Event Generator bit group (CHANNEL.EVGEN)
23.6.2.2 Enabling, Disabling and Resetting
The EVSYS is always enabled.