Section 14 Direct Memory Access Controller (DMAC)
Rev.1.00 Dec. 13, 2005 Page 592 of 1286
REJ09B0158-0100
14.4.2 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 for channels 0 to 5 and DMAOR1 for channels 6 to 11.
If the DMAC receives simultaneous transfer requests from both any channels 0 to 5 and 6 to 11
respectively, then executes each channels 0 to 5 or 6 to 11 request alternately (initial state: channel
0 to 5 is higher priority).
Fixed Mode: In this mode, the priority levels among the channels remain fixed. There are two
kinds of fixed modes as follows:
Channels 0 to 5
•
CH0 > CH1 > CH2 > CH3 > CH4 > CH5
•
CH0 > CH2 > CH3 > CH1 > CH4 > CH5
Channels 6 to 11
•
CH6 > CH7 > CH8 > CH9 > CH10 > CH11
•
CH6 > CH8 > CH9 > CH7 > CH10 > CH11
These are selected by the bits PR[1:0] in DMAOR0 and DMAOR1.
Round-Robin Mode: In round-robin mode each time data of one transfer unit (byte, word,
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 14.2. The priority of round-robin mode is CH0 > CH1 >
CH2 > CH3 > CH4 > CH5, and CH6 > CH7 > CH8 > CH9 > CH10 > CH11 immediately after
reset.
When round-robin mode is specified, do not mix the cycle steal mode and the burst mode in
channels 0 to 5 or 6 to 11 respectively.
Содержание SH7780 Series
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