RX610 Group
12. DMA Controller (DMAC)
R01UH0032EJ0120 Rev.1.20
Page 332 of 1006
Feb 20, 2013
12.5
Low-Power Consumption
If the DMAC is to be placed in any low power-consumption state (module-stop state, all-module clock-stop mode,
software-standby mode, or deep software-standby mode), DMAC transfer in progress when the request for transition to
the low-power state was accepted must be suspended.
Specifically, clear the DMST bit in DMSCNT to 0 (stopping the DMAC) in advance of transitions of the DMAC to the
module-stop state or of the overall device to all-module clock stop mode, software standby mode, or deep software
standby mode.
(1) Module Stop
After "0" has been written to the DMSCNT.DMST (DMAC stop) bit, writing a "1" to the MSTPA28 bit (transition to the
module-stop state) in MSTPCRA places the DMAC in the module-stop state. If DMA transfer is in progress at the time a
"1" is written to the MSTPA28 bit, the transition to the module-stop state proceeds after DMAC transfer has been
suspended. Furthermore, the internal registers of the DMAC become inaccessible at the time a "1" is written to the
MSTPA28 bit, regardless of the state of DMA transfer.
Writing a "0" to the MSTPA28 bit releases the DMAC from the module-stop state. The registers of the DMAC become
accessible again once the DMAC is supplied with a clock signal.
(2) All-Module Clock-Stop Mode
After writing "0" to the DMSCNT.DMST (DMAC stop) bit, and then writing a "1" to the ACSE bit (permitting
all-module clock-stop mode) in MSTPCRA, writing "1" to all bits in MSTPCRA and MSTPCRB, including the
MSTPA28 bit (module-stop bit for the DMAC), and confirming that "1" has been written to all bits of the MSTPCRA
and MSTPCRB registers, executing a WAIT instruction causes a transition to the all-module clock-stop mode. However,
if DMA transfer is in progress at the time the WAIT instruction is executed, the transition to all-module clock stop mode
becomes possible after the suspension of DMA transfer.
Release from all-module clock stop mode is triggered by an external interrupt (the NMI or any of IRQ0 to IRQ15), a
reset by the signal on the RES# pin, or an internal interrupt (from an 8-bit timer or the watchdog timer).
(3) Software Standby and Deep Software Standby Modes
After writing "0" to the DMSCNT.DMST (DMAC stop) bit, and then writing a "1" to the SBYCR.SSBY bit (selecting a
transition to software standby mode following the execution of a WAIT instruction) and a "0" to the DPSBYCR.DPSBY
bit (so that the transition is not to deep software standby mode following the execution of a WAIT instruction), executing
a WAIT instruction places the chip in software standby mode.
However, if DMA transfer is in progress at the time the WAIT instruction is executed, the transition to software-standby
mode becomes possible after the suspension of DMA transfer.
Release from software-standby mode is triggered by an external interrupt (the NMI or any of IRQ0 to IRQ15), a reset by
the signal on the RES# pin, or an internal interrupt (from an eight-bit timer or the watchdog timer).
If the setting of the DPSBY bit is "1" (selecting a transition to deep software standby mode after execution of a WAIT
instruction), the transition is to deep software standby mode.