SAM4L Datasheet, PDF (316/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
16.5.10 Priority
If more than one PDCA channel is requesting transfer at a given time, the PDCA channels are
prioritized by their channel number. Channels with lower numbers have priority over channels
with higher numbers, giving channel zero the highest priority.
16.5.11
Error Handling
If the Memory Address Register (MAR) is set to point to an invalid location in memory, an error
will occur when the PDCA tries to perform a transfer. When an error occurs, the Transfer Error
bit in the Interrupt Status Register (ISR.TERR) will be set and the DMA channel that caused the
error will be stopped. In order to restart the channel, the user must program the Memory
Address Register to a valid address and then write a one to the Error Clear bit in the Control
Register (CR.ECLR). If the Transfer Error interrupt is enabled, an interrupt request will be gener-
ated when a transfer error occurs.
16.5.12
Peripheral Event Trigger
Peripheral events can be used to trigger PDCA channel transfers. Peripheral Event synchroniza-
tions are enabled by writing a one to the Event Trigger bit in the Mode Register (MR.ETRIG).
When set, all DMA requests will be blocked until a peripheral event is received. For each periph-
eral event received, only one data item is transferred. If no DMA requests are pending when a
peripheral event is received, the PDCA will start a transfer as soon as a peripheral event is
detected. If multiple events are received while the PDCA channel is busy transferring data, an
overflow condition will be signaled in the Peripheral Event System. Refer to Section 31. ”Periph-
eral Event Controller (PEVC)” on page 839 for more information.
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