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Section 13 Direct Memory Access Controller (DMAC)
Rev. 4.00 Sep. 14, 2005 Page 440 of 982
REJ09B0023-0400
Bus Mode and Channel Priority Order: When channel 1 is transferring data in burst mode and a
request arrives for transfer on channel 0, which has higher-priority, the data transfer on channel 0
will begin immediately. In this case, if the transfer on channel 0 is also in burst mode, the transfer
on channel 1 will only resume on completion of the transfer on channel 0.
When channel 0 is in cycle steal mode, one transfer-unit of the data on this channel, which has the
higher priority, is transferred. Data is then transferred continuously on channel 1 without releasing
the internal bus. The bus will then switch between the two in this order: channel 1, channel 0,
channel 1, channel 0, etc. That is, the bus state changes so that CPU cycles are for burst-mode
transfer after the data transfer in cycle steal mode has been completed. An example of this is
shown in figure 13.12. When multiple channels are in the burst mode, data transfer on the channel
that has the highest priority is given precedence. When DMA transfer is being performed on
multiple channels, bus mastership is not released to another bus-master device until all of the
competing burst-mode transfers have been completed.
CPU
DMA
CH1
DMA
CH1
DMA
CH0
DMA
CH1
DMA
CH0
DMA
CH1
DMA
CH1
CPU
CH0
CH1
CH0
Cycle-steal mode in
DMAC CH0 and CH1
DMAC CH1
Burst mode
CPU
CPU
Priority: CH0 > CH1
CH0: Cycle-steal mode
CH1: Burst mode
DMAC CH1
Burst mode
Figure 13.12 Bus State when Multiple Channels Are Operating
In the round-robin mode, do not mix channels in the cycle steal and burst modes. In this case,
although the transfer operation on each channel will be performed correctly, switching between
channels might not correctly follow the priority order.
13.4.5
Number of Bus Cycle States and
DREQ
Pin Sampling Timing
Number of Bus Cycle States: When the DMAC is the bus master, the number of bus cycle states
is controlled by the bus state controller (BSC) in the same way as when the CPU is the bus master.
For details, see section 12, Bus State Controller (BSC).
DREQ
Pin Sampling Timing: Figures 13.13 to 13.16 show the
DREQ
input sampling timings in
each bus mode.
Summary of Contents for HD6417641
Page 2: ...Rev 4 00 Sep 14 2005 Page ii of l...
Page 7: ...Rev 4 00 Sep 14 2005 Page vii of l...
Page 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
Page 12: ...Rev 4 00 Sep 14 2005 Page xii of l...
Page 28: ...Rev 4 00 Sep 14 2005 Page xxviii of l...
Page 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Page 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Page 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Page 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Page 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Page 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Page 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Page 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Page 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Page 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Page 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Page 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Page 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
Page 1032: ...Rev 4 00 Sep 14 2005 Page 982 of 982 REJ09B0023 0400 X X Y data addressing 52 X Y memory 193...
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