HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 356

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

10.4.4
When the DMAC receives simultaneous transfer requests on two or more channels, it selects a
channel according to a predetermined priority order. The four modes (fixed mode 1, fixed mode 2,
channel selective round-robin mode, and all-channel round-robin mode) are selected using the bits
PR1 and PR0 in DMAOR.
Fixed Mode: In these modes, the priority levels among the channels remain fixed. There are two
kinds of fixed modes as follows:
These are selected by the bits PR1 and the PR0 in DMAOR.
Round-Robin Mode: Each time one word, byte, longword, or 16-byte 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 10.3. The
priority of the round-robin mode is CH0 > CH1 > CH2 > CH3 immediately after reset. When
round-robin mode is selected, cycle steal mode and burst mode should not be mixed as the bus
mode of two or more channels.
Rev. 1.00, 02/04, page 318 of 804
Channel Priority
Fixed mode 1: CH0 > CH1 > CH2 > CH3
Fixed mode 2: CH0 > CH2 > CH3 > CH1