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7.6.5
Note on Activating DMAC by Internal Interrupts
When using an internal interrupt to activate the DMAC, make sure that the interrupt selected as
the activating source does not occur during the interval after it has been selected but before the
DMAC has been enabled. The on-chip supporting module that will generate the interrupt should
not be activated until the DMAC has been enabled. If the DMAC must be enabled while the on-
chip supporting module is active, follow the procedure in figure 7.26.
Yes
Interrupt hand-
ling by CPU
Figure 7.26 Procedure for Enabling DMAC while On-Chip Supporting
If the DTE bit is set to 1 but the DTME bit is cleared to 0, the DMAC is halted and the selected
activating source cannot generate a CPU interrupt. If the DMAC is halted by an NMI interrupt, for
example, the selected activating source cannot generate CPU interrupts. To terminate DMAC
operations in this state, clear the DTE bit to 0 to allow CPU interrupts to be requested. To continue
DMAC operations, carry out steps 2 and 4 in figure 7.26 before and after setting the DTME bit
to 1.
238
Enabling of DMAC
Selected interrupt
requested?
No
Clear selected interrupt's
enable bit to 0
Enable DMAC
Set selected interrupt's
enable bit to 1
DMAC operates
Module is Operating (Example)
1.
While the DTE bit is cleared to 0,
interrupt requests are sent to the
CPU.
2.
Clear the interrupt enable bit to 0
in the interrupt-generating on-chip
1
supporting module.
3.
Enable the DMAC.
4.
Enable the DMAC-activating
interrupt.
2
3
4
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