Mitsubishi Electric M32R Series User Manual page 269

9
9.4 Precautions about the DMAC
• Manipulating DMAC related registers by DMA transfer
When manipulating DMAC related registers by means of DMA transfer (e.g., reloading the DMAC
related registers' initial values by DMA transfer), do not write to the DMAC related registers on the
local channel itself through that channel. (If this precaution is neglected, device operation cannot be
guaranteed.)
Only if residing on other channels, you can write to the DMAC related registers by means of DMA
transfer. (For example, you can rewrite the DMAn Source Address and DMAn Destination Address
Registers on channel 1 by DMA transfer through channel 0.)
• About the DMA Interrupt Request Status Register
When clearing the DMA Interrupt Request Status Register, be sure to write 1s to all bits but the one
you want to clear. The bits to which you wrote 1s retain the previous data they had before the write.
• About the stable operation of DMA transfer
To ensure the stable operation of DMA transfer, never rewrite the DMAC related registers, except
the DMA Channel Control Register's transfer enable bit, unless transfer is disabled. One exception
is that even when transfer is enabled, you can rewrite the DMA Source Address and DMA
Destination Address Registers by DMA transfer from one channel to another.
9.4 Precautions about the DMAC
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DMAC
Ver.0.10