Dma Arbitration Control Register - Motorola MVME172 Programmer's Reference Manual

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.
ADR/SIZ
BIT
7
NAME 0
OPER
R
RESET 0 R
ROTAT
PRI1,PRI0
PRI1 - PRI0
00
01
10
11
PRI1 - PRI0
00 DMA_a chan 0
01 DMA_a chan 1
10 DMA_c chan 0
11 DMA_c chan 1
http://www.mcg.mot.com/literature
$FFFBC01E (8 bits)
6 5
0 0
R R
0 R 0 R
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
Fixed priority assignment is defined by the following
tables.
Priority with one DMA channel at IP sockets a, b, c, & d
Highest Next Highest
DMA_a DMA_b
DMA_b DMA_c
DMA_c DMA_d
DMA_d DMA_a
Priority with two DMA channel at IP sockets a and c
Highest Next Highest
DMA_a chan 1
DMA_c chan 0
DMA_c chan 1
DMA_a chan 0
4 3 2
0 0 ROTAT
R R R/W
0 R 0 R 0 R
Next Lowest
DMA_c
DMA_d
DMA_a
DMA_b
Next Lowest
DMA_c chan 0
DMA_c chan 1
DMA_a chan 0
DMA_a chan 1
Programming Model
1 0
PRI1 PRI0
R/W R/W
0 R 0 R
Lowest
DMA_d
DMA_a
DMA_b
DMA_c
Lowest
DMA_c chan 1
DMA_a chan 0
DMA_a chan 1
DMA_c chan 0
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