TMPR4925 datasheet(179/590 Pages) TOSHIBA

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Chapter 8 DMA Controller

8-9

During Single Address transfer, the DMA Destination Address Register (DMDARn) and DMA

Destination Address Increment Register (DMDAIRn) settings are ignored.

Table 8.3.2 Channel Register Setting Restrictions During Single Address Transfer

DMSARn[1:0]

Transfer Setting

Size

(DMCCRn.XFSZ)

DMSAIRn is “0” or

greater

DMSAIRn setting is a

negative value

DMSAIRn[1:0]

DMCNTRn[1:0]

1 Byte

2 Bytes

4 Bytes

4 Words

8 Words

16 Words

32 Words

4/0/-4

8.3.7.2

Burst Transfer During Single Address Transfer

According to the SDRAM Controller and External Bus Controller specifications, the DMA

Controller cannot perform Burst transfer that spans across 32 word boundaries. Consequently, if

the address that starts DMA transfer is not a multiple of the transfer setting size (DMCCRn.XFSZ)

(is not aligned), transfer cannot be performed by any of the transfer sizes that were specified by a

Burst transfer. Therefore, the DMA Controller executes multiple Burst transactions of a transfer

size smaller than the specified transfer size. This division method changes according to the seting

of the Transfer Size Mode bit (DMCCRn.USEXFSZ) of the DMA Channel Control Register.

Figure 8.3.2 shows the Single Address Burst transfer status when the lower 7 bits of the

Transfer Start address are 0x54 and the transfer setting size (DMCCRn.XFSZ) is set to 4 words.

Panel (a) of this figure shows the situation when the Transfer Size Mode bit

(DMCCRn.USEXFSZ) is “0”. In this case, first a three word transfer is performed up to the

address aligned to the transfer setting size. Then, four word transfer specified by the transfer

setting size is repeated. This setting is normally used.

On the other hand, panel (b) shows when the Transfer Size Mode bit (DMCCRn.USEXFSWZ)

is “1”. in this case, transfer is repeated according to the transfer setting size. Three word transfer

and one word transfer is only performed consecutively without releasing bus ownership when

transfer spans across a 32 word boundary.

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