193
ch0 > ch3 > ch2 > ch1
ch3 > ch2 > ch1 > ch0
ch0 > ch3 > ch2 > ch1
ch2 > ch1 > ch0 > ch3
ch0 > ch3 > ch2 > ch1
ch1 > ch0 > ch3 > ch2
ch2 > ch1 > ch0 > ch3
ch0 > ch3 > ch2 > ch1
ch0 > ch3 > ch2 > ch1
(1) When channel 0 transfers
Initial priority order
Priority order
after transfer
(2) When channel 3 transfers
Initial priority order
Priority order
after transfer
(3) When channel 2 transfers
Initial priority order
Priority order
after transfer
Priority order after transfer when
there is an immediate transfer
request for channel 3 only
(4) When channel 1 transfers
Initial priority order
Priority order
after transfer
Channel 3 becomes bottom
priority. The priority of channel
0, which was higher than
channel 3, is also shifted.
Channel 0 becomes
bottom priority
Channel 2 becomes bottom
priority. The priority of channels
0 and 3, which were higher than
channel 2, are also shifted.
If immediately thereafter there
is a transfer request for channel
3 only, channel 3 becomes
bottom priority and the priority
of channels 0 and 1, which
were higher than channel 3,
are also shifted.
Priority order does not change
Figure 9.3 Round-Robin Mode
Figure 9.4 shows how the priority order changes when channel 0 and channel 1 transfers are
requested simultaneously and a channel 3 transfer is requested during the channel 0 transfer. The
DMAC operates as follows:
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