TMPR4938 datasheet(187/716 Pages) TOSHIBA

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Chapter 8 DMA Controller

8-13

Table 8.3.3 Channel Register Setting Restrictions During Dual Address Transfer

DMSARn[2:0]

DMDARn[2:0]

Transfer Setting

Size

(DMCCRn.XFSZ)

DMSAIRn

setting is 0

or greater

DMSAIRn

setting is a

negative

value

DMDAIRn

setting is 0

or greater

DMDAIRn

setting is a

negative

value

DMSAIRn DMDAIRn DMCNTRn

DMCCRn

REVBYTE

1 Byte

***

2 Bytes

**0

**1

**0

4 Bytes

*00

*11

*00

8 Bytes,

4 / 8 Double Wods

(DMMCR.FIFUM[n]

=0)

000

111

000

111

000

0/1

000

111

000

111

8/0/-8

8/-8 ‡

000

0/1

***

⎯

***

⎯

4 / 8 Double Words

(DMMCR.FIFUM[n]

=1)

⎯

***

⎯

***

-8

***

16 Double Words

Cannot be set (Configuration Error)

32 Double Words

Cannot be set (Configuration Error)

When DMSAIRn is set to 0, read access from source device is performed only one time per

transmission specified by DMCCRn.XFSZ. For this reason, transfer can not be performed burst

transfer to the I/O device which performs FIFO operation.

‡:

8, 0, or -8 can be specified when the Destination Burst Inhibit bit (DMCCRn.DBINH) is set.

8.3.8.2

Burst Transfer During Dual Address Transfer

The DMA Controller has a 64-bit 8-stage FIFO on-chip that is connected to the internal bus (G-

Bus) for Burst transfer during Dual Address transfer. Since this FIFO employs a shifter, it is

possible to perform transfer of any address or data size. Burst transfer is only performed when 4

Double Words or 8 Double Words is set by the Transfer Setting Size field (DMCCRn.XFSZ) and

the FIFO Use Enable bit (DMMCRn.FIFUM[n]) of the DMA Master Control Register is set.

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

Controller cannot perform Burst transfer that spans across 32-double 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, it is necessary to divide the transfer into 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 and whether or not the address offset relative to the Transfer Setting size

(DMCCRn.XFSZ) is equivalent to the source address and destination address combined.

Figure 8.3.3 shows Dual Address Burst transfer when the Transfer Size Mode bit

(DMCCRn.USEXFSZ) is set to “1”, the lower 8 bits of the Transfer Start address for the transfer

source are set to 0xA8, the lower 8 bits of the Transfer Start address for the transfer destination are

set to 0x38, and the Transfer Setting Size (DMCCRn.XFSZ) is set to 8 Double Words.

Transfer repeats according to the transfer setting size, regardless of the different address offsets.

However, transfers that span across 32-double word boundaries are divided. Since data remains in

the on-chip FIFO when in this mode, it becomes possible to share the on-chip FIFO among

multiple DMA channels.

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