SH7764 Datasheet, PDF (444/1752 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A 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 DMAOR0.
(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 DMAOR0
(2) Round-Robin Mode
In round-robin mode each time data of one transfer unit (word, byte, longword, 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 Nov. 22, 2007 Page 388 of 1692
REJ09B0360-0100