H8SSLASH2214 datasheet(295/936 Pages) RENESAS

295 / 936 page

Section 7 DMA Controller

Rev.4.00 Sep. 18, 2008 Page 235 of 872

REJ09B0189-0400

(3) Full Address Mode (Burst Mode)

Figure 7.18 shows a transfer example in which

TEND output is enabled and word-size full address

mode transfer (burst mode) is performed from external 16-bit, 2-state access space to external 16-

bit, 2-state access space.

DMA

read

Address bus

LWR

TEND

HWR

Bus release

DMA

write

DMA

dead

DMA

read

DMA

write

DMA

read

DMA

write

Bus release

Burst transfer

Last transfer cycle

Figure 7.18 Example of Full Address Mode (Burst Mode) Transfer

In burst mode, one-byte or one-word transfers are executed consecutively until transfer ends.

In the transfer end cycle (the cycle in which the transfer counter reaches 0), a one-state DMA dead

cycle is inserted after the DMA write cycle.

If a request from another higher-priority channel is generated after burst transfer starts, that

channel has to wait until the burst transfer ends.

If an NMI is generated while a channel designated for burst transfer is in the transfer enabled state,

the DTME bit is cleared and the channel is placed in the transfer disabled state. If burst transfer

has already been activated inside the DMAC, the bus is released on completion of a one-byte or

one-word transfer within the burst transfer, and burst transfer is suspended. If the last transfer

cycle of the burst transfer has already been activated inside the DMAC, execution continues to the

end of the transfer even if the DTME bit is cleared.

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