SH7205 Datasheet, PDF (483/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 11 Direct Memory Access Controller (DMAC)
11.11 Reload Function
To set the reload function, set each reload function enable bit of DMA control register A
(DMCNTAn) per channel and per transfer parameter (source address, destination address or byte
count).
To configure the reloading function on a channel supporting two-dimensional addressing, set the
two-dimensional reload function enable bit (2DRLOD) of DMA control register A (DMCNTAn)
for the corresponding channel. This enables reloading of the six registers related to two-
dimensional addressing: column setting register, row setting register, block setting register, next
row offset register, next block offset register, and next line offset register.
When the DMA transfer end condition is detected, DMA transfer parameters are automatically
reloaded.
(1) Reload Register and Current Register
When not using the reload function, set data in the current register. When using the reload
function, set data both in the reload register and current register.
Do not write data to the current register during single operand transfer. If data is written to the
current register, operation is not guaranteed. The reload register can be set even during single
operand transfer but this setting must be made before start of the last operand transfer (DMA
transfer end). If the reload register is set after start of the last operand transfer, however, this
setting may have not been reflected when data is reloaded after DMA transfer end.
(2) Continuous Transfer to Dispersed Areas
The reload function provides continuous transfer to dispersed areas. Writing values to the DMA
reload source and destination address registers (DMRSADRn/DMRDADRn) and DMA reload
byte count register (DMRBCTn) before DMA transfer ends enables you to prepare the next
transfer parameters without affecting the current DMA transfer (current register). This enables you
to continuously transfer several transfer blocks in different transfer areas and with a different
number of bytes through the same channel.
Figure 11.14 shows an example of how the reload function transfers blocks between dispersed
areas.
Rev. 1.00 Mar. 25, 2008 Page 451 of 1868
REJ09B0372-0100