3069RF-ZTAT Datasheet, PDF (271/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

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.
Enabling of DMAC
Yes
Interrupt hand-
ling by CPU
Selected interrupt
requested?
No
Clear selected interrupt's
enable bit to 0
[1] While the DTE bit is cleared to 0,
interrupt requests are sent to the
CPU.
[2] Clear the interrupt enable bit to 0
[1]
in the interrupt-generating on-chip
supporting module.
[3] Enable the DMAC.
[4] Enable the DMAC-activating
interrupt.
[2]
Enable DMAC
[3]
Set selected interrupt's
[4]
enable bit to 1
DMAC operates
Figure 7.26 Procedure for Enabling DMAC while On-Chip Supporting
Module is Operating (Example)
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.
Rev. 5.0, 09/04, page 249 of 978