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RL78/G1A CHAPTER 15 DMA CONTROLLER
15.5.5 Forced termination by software
After the DSTn bit is set to 0 by software, it takes up to 2 clocks until a DMA transfer is actually stopped and the DSTn
bit is set to 0. To forcibly terminate a DMA transfer by software without waiting for occurrence of the interrupt (INTDMAn)
of DMAn, therefore, perform either of the following processes.
<When using one DMA channel>
• Set the DSTn bit to 0 (use DRCn = 80H to write with an 8-bit manipulation instruction) by software, confirm by polling
that the DSTn bit has actually been cleared to 0, and then set the DENn bit to 0 (use DRCn = 00H to write with an 8-
bit manipulation instruction).
• Set the DSTn bit to 0 (use DRCn = 80H to write with an 8-bit manipulation instruction) by software and then set the
DENn bit to 0 (use DRCn = 00H to write with an 8-bit manipulation instruction) two or more clocks after.
<When using two or more DMA channels>
• To forcibly terminate DMA transfer by software when using two or more DMA channels (by setting DSTn to 0), clear
the DSTn bit to 0 after the DMA transfer is held pending by setting the DWAITn bits of all using channels to 1. Next,
clear the DWAITn bits of all using channels to 0 to cancel the pending status, and then clear the DENn bit to 0.
Figure 15-11. Forced Termination of DMA Transfer (1/2)
Example 1 Example 2
DSTn = 0
DENn = 0
DSTn = 0?
No
2 clock wait
Yes
DSTn = 0
DENn = 0
Remarks 1. n: DMA channel number (n = 0, 1)
2. 1 clock: 1/f
CLK (fCLK: CPU clock)
R01UH0305EJ0200 Rev.2.00 683
Jul 04, 2013