SH7261 datasheet(399/1348 Pages) RENESAS

399 / 1348 page

Section 11 Direct Memory Access Controller (DMAC)

Rev. 2.00 Sep. 07, 2007 Page 367 of 1312

REJ09B0320-0200

11.10

Reload Function

Reloading can be set up for each transfer parameter (source address, destination address, or byte

count) of a channel through the setting of the individual reload function enable bits in the

corresponding DMA control register A (DMCNTAn). When the DMA transfer end condition is

detected, DMA transfer parameters specified for reloading are automatically reloaded.

(1)

Reload and Current Registers

If reloading is not in use, only place the data in the current register. When reloading is in use,

place data in both the reload and current registers.

Do not write to the current register during single operand transfer. If data is written to the register

during continuous operation, further operation is not guaranteed. Although the reload register can

be set during single operand transfer, ensure that this is not the last single operand transfer of a

DMA transfer. If the setting is executed after that point, the new setting may not be reloaded on

completion of the DMA transfer.

(2)

Continuous Transfer to Dispersed areas

The reload function enables continuous transfer to dispersed areas.

Writing to the DMA reload source/destination address register (DMRSADRn/ DMRDADRn) or

the DMA reload byte count register (DMRBCTn) before the completion of transfer provides a way

of preparing the parameters for the next transfer without affecting the current DMA transfer

(current registers). This enables the use of a single channel for the continuous transfer of multiple

transfer blocks consisting of different numbers of bytes to and from different transfer areas over a

single channel.

Figure 11.13 shows an example of the transfer of blocks between dispersed areas with the aid of

the reload function.

SH7261 Datasheet(PDF) 399 Page - Renesas Technology Corp