SH7710 Datasheet, PDF (522/996 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 13 Direct Memory Access Controller (DMAC)
Round-Robin Mode: Each time one word, byte, longword or 16-byte unit is transferred on one
channel, the priority order is rotated. The channel on which the transfer was just finished rotates to
the bottom of the priority order. The round-robin mode operation is shown in figure 13.3. The
priority of the round-robin mode is CH0 > CH1 > CH2 > CH3 > CH4 > CH5 immediately after a
reset. When round-robin mode is specified, the bus mode setting of multiple channels does not
allow a mixture of cycle steal mode and burst mode.
(1) When channel 0 transfers
Initial priority order _{CH0 > CH1 > CH2 > CH3 > CH4 > CH5}
Channel 0 becomes bottom
priority
Priority order
afrer transfer
CH1 > CH2 > CH3 > CH4 > CH5 > CH0
(2) When channel 1 transfers
Initial priority order
Priority order
afrer transfer
CH0 > CH1 > CH2 > CH3 > CH4 > CH5
CH2 > CH3 > CH4 > CH5 > 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 transfers
Initial priority order CH0 > CH1 > CH2 > CH3 > CH4 > CH5
Priority order
afrer transfer
CH3 > CH4 > CH5 > CH0 > CH1 > CH2
Post-transfer priority order
when there is an
immediate transfer
request to channel 5 only
CH0 > CH1 > CH2 > CH3 > CH4 > CH5
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 5 only, channel 5 becomes
bottom priority and the priority of
channels 3 and 4, which were
higher than channel 5, are also
shifted.
(4) When channel 5 transfers
Initial priority
order
Priority order
afrer transfer
CH0 > CH1 > CH2 > CH3 > CH4 > CH5
CH0 > CH1 > CH2 > CH3 > CH4 > CH5
Priority order does not change
Figure 13.3 Round-Robin Mode
Rev. 2.00 Dec. 07, 2005 Page 480 of 950
REJ09B0079-0200