H8SSLASH2224 datasheet(327/1071 Pages) RENESAS

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Section 8 DMA Controller (DMAC)

Rev. 5.00 Aug 08, 2006 page 241 of 982

REJ09B0054-0500

8.5.4

Repeat Mode

Repeat mode can be specified by setting the RPE bit in DMACR to 1, and clearing the DTIE bit in

DMABCRL to 0. In repeat mode, MAR is updated after each byte or word transfer in response to

a single transfer request, and this is executed the number of times specified in ETCRL. On

completion of the specified number of transfers, MAR and ETCRL are automatically restored to

their original settings and operation continues. One address is specified by MAR, and the other by

IOAR. The transfer direction can be specified by the DTDIR bit in DMACR. Table 8.7

summarizes register functions in repeat mode.

Table 8.7

Function

DTDIR = 0 DTDIR = 1 Initial Setting

Operation

MAR

Source

address

Destination

address

Start address of

transfer destination

or transfer source

Incremented/

decremented every

transfer

Initial setting is

restored when value

reaches H'0000

IOAR

H'FF

Destination

address

Source

address

Start address of

transfer source or

transfer destination

Fixed

ETCRH

Holds number of

transfers

Number of transfers Fixed

ETCRL

Transfer counter

Number of transfers Decremented every

transfer

Loaded with ETCRH

value when count

reaches H'00

MAR specifies the start address of the transfer source or transfer destination as 24 bits. MAR is

incremented or decremented by 1 or 2 each time a byte or word is transferred. IOAR specifies the

lower 16 bits of the other address. The upper 8 bits of IOAR have a value of H'FF. The number of

transfers is specified as 8 bits by ETCRH and ETCRL. The maximum number of transfers, when

H'00 is set in both ETCRH and ETCRL, is 256.

In repeat mode, ETCRL functions as the transfer counter, and ETCRH is used to hold the number

of transfers. ETCRL is decremented by 1 each time a data transfer is executed, and when its value

reaches H'00, it is loaded with the value in ETCRH. At the same time, the value set in MAR is

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