SH7619_09 Datasheet, PDF (386/860 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7619 Series

Section 13 Direct Memory Access Controller (DMAC)
Round-Robin Mode: In round-robin mode each time data of one transfer unit (word, byte,
longword, or 16-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 13.3. The priority of round-robin mode is CH0 > CH1 > CH2 > CH3
immediately after a reset. When round-robin mode is specified, the same bus mode, either cycle
steal mode or burst mode, must be specified for all of the channels.
(1) When channel 0 is transferred
Initial priority order _{CH0 > CH1 > CH2 > CH3}
Priority order
after transfer
CH1 > CH2 > CH3 > CH0
Channel 0 becomes bottom
priority
(2) When channel 1 is transferred
Initial priority order
Priority order
after transfer
CH0 > CH1 > CH2 > CH3
CH2 > CH3 > CH0 > CH1
Channel 1 becomes bottom
priority.
The priority of channel 0, which
was higher than channel 1, is also
shifted.
(3) When channel 2 is transferred
Initial priority order CH0 > CH1 > CH2 > CH3
Priority order
after transfer
CH3 > CH0 > CH1 > CH2
Post-transfer priority order
when there is an
immediate transfer
request to channel 1 only
CH2 > CH3 > CH0 > CH1
Channel 2 becomes bottom
priority.
The priority of channels 0 and 1,
which were higher than channel 2,
are also shifted. If immediately
after there is a request to transfer
channel 1 only, channel 1 becomes
bottom priority and the priority of
channels 0 and 3, which were
higher than channel 1, are also
shifted.
(4) When a channel 3 is transferred
Initial priority order _{CH0 > CH1 > CH2 > CH3}
Priority order does not change.
Priority order
after transfer
CH0 > CH1 > CH2 > CH3
Figure 13.3 Round-Robin Mode
Rev. 6.00 Jul. 15, 2009 Page 346 of 816
REJ09B0237-0600