7721 datasheet(319/577 Pages) RENESAS

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7721 Group User’s Manual

13-40

DMA CONTROLLER

13.4 Operation

(1)

Figure 13.4.6 shows a basic operation of registers for 1-unit transfer in 1-bus cycle transfer. For

Link array chain transfer mode.” It is because these values vary depending on each continuous

transfer mode. In 1-bus cycle transfer, a read and write of 1-transfer-unit data are simultaneously

performed during 1-bus cycle.

Fig. 13.4.6 Basic operation of registers for 1-unit transfer in 1-bus cycle transfer

Transfer source address is specified by DARi (Note).

Contents of TCRi are updated by decrementer (Note);

when value read from TCRi is “0,” transfer of 1 data

block is terminated.

Contents of DARi are updated by incrementer/

decrementer.

I/O is specified by DMAACKi.

Data is output from I/O and is written to memory

simultaneously (R/W = L level).

Transfer source address is specified by SARi

(Note).

Contents of TCRi are updated by decrementer

(Note); when value read from TCRi is “0,” transfer

of 1 data block is terminated.

Contents of SARi are updated by incrementer/

decrementer.

I/O is specified by DMAACKi.

Data is output from memory and is written to I/O

simultaneously (R/W = H level).

qWhen transferring from memory to I/O

SARi

SARi latch

DMA latch

DMAC

Memory

(Transfer

source)

DMAC

I/O

DMAACKi

I/O

DARi

DARi latch

TCRi

TCRi latch

(Transfer

destination)

Incrementer/

Decrementer

qWhen transferring from I/O to memory

Memory

SARi

SARi latch

DMA latch

DMAACKi

DARi

DARi latch

TCRi

TCRi latch

Incrementer/

Decrementer

(Transfer

source)

(Transfer

destination)

V When the transfer unit is 16 bits, the incrementer/decrementer and the decrementer increment or decrement by 2.

Note: In the single transfer mode and repeat transfer mode, only at the first transfer of the block, the values read

from SARi latch, DARi latch, and TCRi latch are used. (The results obtained by increment or decrement are

written to SARi, DARi, and TCRi. Except for the first transfer of the block, the values read from SARi, DARi,

and TCRi are used.)

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