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13.4 Operations of the DMA Controller
A multifunctional DMA controller is built in the FR30 Series to control data transfer at
high speed without CPU instructions.
s Outline of DMA Controller Operations
Functions are set independently to each transfer channel.
Once a channel has been activated, the transfer operation continues until the set transfer
request is detected.
When the transfer request is detected, this module issues a hold request to the CPU and
acquires each bus privilege to start transfer.
The transfer procedure follows the sequence set independently for each channel.
Step/block transfer:
Transfer is executed once only on a transfer request.
The bus
privilege is released (returned) until the next transfer request is received.
Burst transfer: Transfer is executed a specified number of times on a transfer request.
Continuous transfer:
Transfer is executed a specified number of times or until the
external transfer request input (level detection) is finished.
Addressing of the following type is set independently for the source and destination of each
channel.
Address register specification: A read value from a register where an addresses is preset
(address register) is used for access. The address counter determines the next access
address (Increment, Decrement, or Fixed) at each access and returns the address to the
counter.
The transfer count register is decremented (-1) at the end of each transfer.
Once the
register value has become 0 after the specified number of transfer repetitions, this module
terminates or reactivates the channel with the end code.
The transfer termination resources are as follows (at termination, the corresponding resource
is displayed as a end code):
Transfer repeated the specified number of times (Normal termination)
Transfer stop request from peripheral circuit, address error, or reset
Transfer end interrupt or error interrupt depending on the termination resource
s Common Symbols of the DMA Controller
The following symbols are used in drawings related to DMA controller operations:
CPU: Bus use by CPU
Source address: Transfer-from address
Destination address: Transfer-to address
s Basic Operation Flow Chart of the DMA Controller
Figure 13.4.1 shows a basic operation flow chart of the DMA controller.