SH7730 Datasheet, PDF (479/1188 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7780 Series

Section 12 Direct Memory Access Controller (DMAC)
12.4.2 Channel Priority
When the DMAC receives simultaneous transfer requests on two or more channels, it transfers
data according to a predetermined priority. Two modes (fixed mode and round-robin mode) are
selected by the bits PR[1:0] in DMAOR.
(1) Fixed Mode
In this mode, the priority levels among the channels remain fixed. There are two kinds of fixed
modes as follows:
• CH0 > CH1 > CH2 > CH3 > CH4 > CH5
• CH0 > CH2 > CH3 > CH1 > CH4 > CH5
These are selected by the bits PR[1:0] in DMAOR.
(2) Round-Robin Mode
In round-robin mode each time data of one transfer unit (byte, word, longword, 8-byte, 16-byte,
or 32-byte unit) is transferred on one channel, the priority is rotated. The channel on which the
transfer was just finished rotates to the bottom of the priority. The round-robin mode operation is
shown in figure 12.2. The priority of round-robin mode is CH0 > CH1 > CH2 > CH3 > CH4 >
CH5 immediately after reset.
When round-robin mode is specified, do not mix the cycle steal mode and the burst mode in
multiple channels' bus modes.
Rev. 1.00 Sep. 19, 2007 Page 431 of 1136
REJ09B0359-0100