Section 9 Direct Memory Access Controller (DMAC)
Rev. 5.00 May 29, 2006 page 269 of 698
REJ09B0146-0500
The DMA transfer request signals of table 9.3 are automatically withdrawn when the
corresponding DMA transfer is performed. If the cycle-steal mode is being used, they are
withdrawn at the first transfer; if the burst mode is being used, they are withdrawn at the last
transfer.
9.4.3
Channel Priority
When the DMAC receives simultaneous transfer requests on two or more channels, it selects a
channel according to a predetermined priority order. Two modes (fixed mode and round-robin
mode) are selected by the priority bits PR1 and PR0 in the DMA operation register (DMAOR).
Fixed Mode: In this mode, the priority levels among the channels remain fixed. There are three
kinds of fixed modes as follows:
•
CH0 > CH1 > CH2 > CH3
•
CH0 > CH2 > CH3 > CH1
•
CH2 > CH0 > CH1 > CH3
These are selected by the PR1 and the PR0 bits in the DMA operation register (DMAOR).
Round-Robin Mode: Each time one word, byte, or longword, or 16-byte data 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 9.3.
The priority of the round-robin mode is CH0 > CH1 > CH2 > CH3 immediately after a reset.
Содержание SH7706 Series
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Страница 160: ...Section 5 Cache Rev 5 00 May 29 2006 page 112 of 698 REJ09B0146 0500 ...
Страница 370: ...Section 11 Watchdog Timer WDT Rev 5 00 May 29 2006 page 322 of 698 REJ09B0146 0500 ...
Страница 532: ...Section 16 Serial Communication Interface with FIFO SCIF Rev 5 00 May 29 2006 page 484 of 698 REJ09B0146 0500 ...
Страница 554: ...Section 17 Pin Function Controller PFC Rev 5 00 May 29 2006 page 506 of 698 REJ09B0146 0500 ...
Страница 576: ...Section 18 I O Ports Rev 5 00 May 29 2006 page 528 of 698 REJ09B0146 0500 ...
Страница 614: ...Section 21 User Debugging Interface H UDI Rev 5 00 May 29 2006 page 566 of 698 REJ09B0146 0500 ...
Страница 746: ...Index Rev 5 00 May 29 2006 page 698 of 698 REJ09B0146 0500 ...
Страница 749: ...SH7706 Group Hardware Manual ...