SH7727 Datasheet, PDF (474/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

Section 14 Direct Memory Access Controller (DMAC)
In order to output a transfer request from an on-chip supporting module, set the corresponding
interrupt enable bit for outputting the interrupt signal.
When the interrupt request signal from an on-chip supporting module is used as a DMA transfer
request signal, an interrupt is not generated to the CPU.
The DMA transfer request signals shown in table 14.4 are automatically canceled when the
corresponding DMA transfer is completed. This operation is provided at the first transfer in cycle
steal mode, and at the last transfer in burst mode.
14.3.3 Channel Priority
When the DMAC receives multiple transfer requests simultaneously, it provides transfer operation
according to a specified priority order. The fixed mode or round-robin mode can be selected for
the channel priority with the PR1 and PR0 bit in the DMA operation register (DMAOR).
Fixed Mode: The channel priority is fixed. There are three kinds of orders as follows:
CH0 > CH1 > CH2 > CH3
CH0 > CH2 > CH3 > CH1
CH2 > CH0 > CH1 > CH3
The priority is selected by the PR1 and PR0 bits in the DMA operation register (DMAOR).
Round-Robin Mode: The priority order is rotated each time one transfer unit (word, byte, or
longword) of data has been transferred. The channel on which the transfer was just finished is
located at the lowest in priority. The round-robin mode operation is shown in figure 14.3. The
priority of the round-robin mode is CH0 > CH1 > CH2 > CH3 immediately after a reset.
Rev. 5.00 Dec 12, 2005 page 402 of 1034
REJ09B0254-0500