Figure 14.4 Example Of Changes In Priority Order In Round Robin Mode - Hitachi SH7751 Hardware Manual

1. Transfer requests are issued simultaneously for channels 0 and 3.
2. Since channel 0 has a higher priority level than channel 3, the channel 0 transfer is executed
first (channel 3 is on transfer standby).
3. A transfer request is issued for channel 1 during the channel 0 transfer (channels 1 and 3 are on
transfer standby).
4. At the end of the channel 0 transfer, channel 0 shifts to the lowest priority level.
5. At this point, channel 1 has a higher priority level than channel 3, so the channel 1 transfer is
started (channel 3 is on transfer standby).
6. At the end of the channel 1 transfer, channel 1 shifts to the lowest priority level.
7. The channel 3 transfer is started.
8. At the end of the channel 3 transfer, the channel 3 and channel 2 priority levels are lowered,
giving channel 3 the lowest priority.
Transfer request
1. Issued for channels 0
and 3
3. Issued for channel 1

Figure 14.4 Example of Changes in Priority Order in Round Robin Mode

Rev. 3.0, 04/02, page 492 of 1064
Channel DMAC operation
waiting
2. Start of channel 0
transfer
3
4. End of channel 0
1, 3
transfer
5. Start of channel 1
transfer
6. End of channel 1
3
transfer
7. Start of channel 3
transfer
None
8. End of channel 3
transfer
Channel priority
order
0 > 1 > 2 > 3
Change of
priority order
1 > 2 > 3 > 0
Change of
priority order
2 > 3 > 0 > 1
Change of
priority order
0 > 1 > 2 > 3