SH7201 Datasheet, PDF (391/1196 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 11 Direct Memory Access Controller (DMAC)
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.
Rev. 2.00 Sep. 07, 2007 Page 363 of 1164
REJ09B0321-0200