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7.5.7
DMAC Activation Sources
DMAC activation sources consist of internal interrupts, external requests, and auto-requests. The
activation sources that can be specified depend on the transfer mode and the channel, as shown in
table 7-12.
Table 7-12 DMAC Activation Sources
Short Address Mode
Full Address Mode
Activation Source
Channels
0A and 1A
Channels
0B and 1B
Normal
Mode
Block
Transfer
Mode
Internal
TXI0
X
Interrupts
RXI0
X
TXI1
X
RXI1
X
TGI0A
X
TGI1A
X
TGI2A
X
External
DREQ pin falling edge input
X
Requests
DREQ pin low-level input
X
Auto-request
X
Legend
: Can be specified
X : Cannot be specified
Activation by Internal Interrupt: An interrupt request selected as a DMAC activation source
can be sent simultaneously to the CPU and DTC. For details, see section 5, Interrupt Controller.
With activation by an internal interrupt, the DMAC accepts the request independently of the
interrupt controller. Consequently, interrupt controller priority settings are not accepted.
If the DMAC is activated by a CPU interrupt source or an interrupt source that is not used as a
DTC activation source (DTA = 1), the interrupt source flag is cleared automatically by the DMA
transfer. With TXI and RXI interrupts, however, the interrupt source flag is not cleared unless the
prescribed register is accessed in a DMA transfer. If the same interrupt is used as an activation
source for more than one channel, the interrupt request flag is cleared when the highest-priority
channel is activated first. Transfer requests for other channels are held pending in the DMAC, and
activation is carried out in order of priority.