Motorola MVME172 - Manual (Page 265)

Programming Model
http://www.mcg.mot.com/literature 4-29
4
DMA Arbitration Control Register
The DMA arbitration control register contents determine whether a fixed
or fair arbitration algorithm is used to determine how the MC68060 local
bus is attached to the internal DMA data paths.
ROTAT ROTAT set to a zero enables a rotating arbitration method
where each DMAC has equal access to the MC68060
local bus. If ROTAT is set to a one, the priority is fixed
according to the following table
PRI1,PRI0 Fixed priority assignment is defined by the following
tables.
ADR/SIZ $FFFBC01E (8 bits)
BIT 7 6 5 4 3 2 1 0
NAME 0 0 0 0 0 ROTAT PRI1 PRI0
OPER R R R R R R/W R/W R/W
RESET 0 R 0 R 0 R 0 R 0 R 0 R 0 R 0 R
PRI1 - PRI0
Priority with one DMA channel at IP sockets a, b, c, & d
Highest Next Highest Next Lowest Lowest
00 DMA_a DMA_b DMA_c DMA_d
01 DMA_b DMA_c DMA_d DMA_a
10 DMA_c DMA_d DMA_a DMA_b
11 DMA_d DMA_a DMA_b DMA_c
PRI1 - PRI0
Priority with two DMA channel at IP sockets a and c
Highest Next Highest Next Lowest Lowest
00 DMA_a chan 0 DMA_a chan 1 DMA_c chan 0 DMA_c chan 1
01 DMA_a chan 1 DMA_c chan 0 DMA_c chan 1 DMA_a chan 0
10 DMA_c chan 0 DMA_c chan 1 DMA_a chan 0 DMA_a chan 1
11 DMA_c chan 1 DMA_a chan 0 DMA_a chan 1 DMA_c chan 0