R01UH0823EJ0100 Rev.1.00 Page 377 of 1823
Jul 31, 2019
RX23W Group 18. DMA Controller (DMACA)
18.7 Low Power Consumption Function
Before transition to the module stop state or software standby mode, clear the DMAST.DMST bit to 0 (DMAC activation
is disabled), and then perform the following.
(1) Module Stop Function
Writing 1 to the MSTPA28 bit (transition to the module-stop state) in MSTPCRA enables the module-stop function of
the DMAC. If DMA transfer is in progress at the time 1 is written to the MSTPA28 bit, the transition to the module-stop
state proceeds after DMA transfer has ended. While the MSTPA28 bit is 1, accessing the DMAC registers are prohibited.
Writing 0 to the MSTPA28 bit releases the DMAC from the module-stop state.
(2) Software Standby
Make settings in accord with the procedure under section 11.6.3.1, Entry to Software Standby Mode in section 11,
Low Power Consumption
.
If DMA transfer operations are in progress at the time the WAIT instruction is executed, the transition to software
standby follows the completion of DMA transfer.
(3) Note on Low Power Consumption Function
For the WAIT instruction and the register setting procedure, see section 11.7.5, Timing of WAIT Instructions in
section 11, Low Power Consumption.
To perform DMA transfer after returning from low power consumption mode, set the DMST bit in DMAST to 1 again.
To use a request that is generated in software standby mode as an interrupt request to the CPU but not as a DMAC startup
request, specify the CPU as the interrupt request destination in accordance with the description in
section 15.4.3,
Selecting Interrupt Request Destinations
in section 15, Interrupt Controller (ICUb), and then execute the WAIT
instruction.
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