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RL78/G1A CHAPTER 15 DMA CONTROLLER
15.4 Operation of DMA Controller
15.4.1 Operation procedure
<1> The DMA controller is enabled to operate when DENn = 1. Before writing the other registers, be sure to set the
DENn bit to 1. Use 80H to write with an 8-bit manipulation instruction.
<2> Set an SFR address, a RAM address, the number of times of transfer, and a transfer mode of DMA transfer to
DMA SFR address register n (DSAn), DMA RAM address register n (DRAn), DMA byte count register n (DBCn),
and DMA mode control register n (DMCn).
<3> The DMA controller waits for a DMA trigger when DSTn = 1. Use 81H to write with an 8-bit manipulation
instruction.
<4> When a software trigger (STGn) or a start source trigger specified by the IFCn3 to IFCn0 bits is input, a DMA
transfer is started.
<5> Transfer is completed when the number of times of transfer set by the DBCn register reaches 0, and transfer is
automatically terminated by occurrence of an interrupt (INTDMAn).
<6> Stop the operation of the DMA controller by clearing the DENn bit to 0 when the DMA controller is not used.
Figure 15-6. Operation Procedure
No
No
DSTn = 1
DSTn = 0
INTDMAn = 1
DMA trigger = 1?
DBCn = 0000H ?
Yes
Yes
DENn = 1
Setting DSAn, DRAn, DBCn, and DMCn
Transmitting DMA request
Receiving DMA acknowledge
DMA transfer
DRAn = DRAn + 1 (or + 2)
DBCn = DBCn − 1
DENn = 0
Set by software program
Operation by DMA
controller (hardware)
Set by software program
Remark n: DMA channel number (n = 0, 1)
R01UH0305EJ0200 Rev.2.00 675
Jul 04, 2013