Fujitsu FR60 Hardware Manual page 512

CHAPTER 16 DMA CONTROLLER (DMAC)
■ Transfer Type
●
2-cycle transfer (normal transfer)
The DMA controller operates using as its unit of operation a read operation and a write operation.
Data is read from an address in the transfer source register and then written to another address in the
transfer destination register.
●
Fly-by transfer (memory → I/O)
Note: The MB91F353A/351A/352A/353A do not support fly-by transfer.
The DMA controller operates using as its unit of operation a read operation.
If DMA transfer is performed when fly-by transfer is set, DMA issues a fly-by transfer (read) request to the
bus controller and the bus controller lets the external interface carry out the fly-by transfer (read).
●
Fly-by transfer (I/O → memory)
Note: The MB91F353A/351A/352A/353A do not support fly-by transfer.
The DMA controller operates using as its unit of operation a write operation.
Otherwise, operation is the same as fly-by transfer (memory → I/O) operation.
Access areas used for MB91F355A/F356B/F357B/355A fly-by transfer must be external areas.
■ Transfer Address
The following types of addressing are available and can be set independently for each channel transfer
source and transfer destination.
The method for specifying the address setting register (DMASA/DMADA) for a 2-cycle transfer and the
method for a fly-by transfer are different.
●
Specifying the address for a 2-cycle transfer
The value read from a register (DMASA/DMADA) in which an address has been set in advance is used as
the address for access. After receiving a transfer request, DMA stores the address from the register in the
temporary storage buffer and then starts transfer.
After each transfer (access) operation, the next access address is generated (increment/decrement/fixed
selectable) by the address counter and then restored to the temporary storage buffer. Because the contents
of the temporary storage buffer are written back to the register (DMASA/DMADA) after each block
transfer unit is completed, the address register (DMASA/DMADA) value is updated after each block
transfer unit is completed, making it impossible to determine the address in real time during transfer.
●
Specifying the address for a fly-by transfer
Note: The MB91F353A/351A/352A/353A do not support fly-by transfer.
In a fly-by transfer, the value read from the transfer destination address register (DMADA) is used as the
address for access. The transfer source address register (DMASA) is ignored. Be sure to specify an external
area as the address to be set.
After receiving a transfer request, DMA stores the address from the register in the temporary storage buffer
and then starts transfer.
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