Overview of Operation
This section provides an overview of DMAC operation.
■ Main DMAC Operations
Functions can be set for each transfer channel independently.
Once starting has been enabled, a channel starts transfer operation only after a specified transfer request has
After a transfer request is detected, a DMA transfer request is outputted to the bus controller and the bus
right is acquired by the bus controller before the transfer is started. The transfer is carried out as a sequence
conforming to the mode settings made independently for the channel being used.
■ Transfer Mode
Each DMA channel performs transfer according to the transfer mode set by the MOD[1:0] bits of its
Only a single block transfer unit is transferred in response to one transfer request. DMA then stops
requesting the bus controller for transfer until the next transfer request is received.
The block transfer unit is the specified block size: (BLK[3:0] of DMACA).
Transfer in response to one transfer request is carried out continuously for the number of times in the
specified transfer count.
The specified transfer count is the transfer count: (BLK[3:0] of DMACA X DTC[15:0] of DMACA) X
Note: The MB91F353A/351A/352A/353A do not support demand transfer.
Transfer is carried out continuously until the transfer request input (detected with a level at the DREQ pin)
from an external device ends or a specified transfer count is reached.
The specified transfer count in a demand transfer is the specified transfer count: (DTC[15:0] of DMACA).
The block size is always "1" and the register value is ignored.