Chapter 9: DMA Controller
TX7901 User’s Manual (Rev. 6.30T – Nov, 2001)
9-5
For example, Figure 9-2 illustrates a situation in which DMA channel 5 is programmed in the
slice mode, and it requires two slice transfers or five DMA bus cycles to finish the data
transfer.
DMA Bus
Cycle #1
SLICE #1
DMA Bus
Cycle #2
DMA Bus
Cycle #3
DMA Bus
Cycle #1
SLICE #2
DMA Bus
Cycle #2
Figure 9-2 DMA Channel 5
When DMA channel 5 is active and cycle stealing is enabled, the C790 can use itself in the
middle of a DMA slice cycle. Figure 9-3 shows the sequence of operations on the C790 bus
for this scenario. The completion interrupt is generated after Slice #2 DMA Bus Cycle #2
finishes.
DMA Bus
Cycle #1
C790 Bus
Cycle
DMA Bus
Cycle #3
DMA Bus
Cycle #1
DMA Bus
Cycle #2
DMA Bus
Cycle #2
C790 Bus
Cycle
SLICE #1
SLICE #2
Figure 9-3 C790 Bus Operations With Cycle Stealing
When DMA channel 5 is active and cycle stealing is disabled, the C790 can use itself only
between the slice transfers. Figure 9-4 shows the sequence of operations on the C790 bus
for this scenario. The completion interrupt is generated after Slice #2 DMA Bus Cycle #2
finishes.
DMA Bus
Cycle #1
C790 Bus
Cycle
DMA Bus
Cycle #3
DMA Bus
Cycle #1
DMA Bus
Cycle #2
DMA Bus
Cycle #2
C790 Bus
Cycle
Slice #1
Slice #2
Figure 9-4 C790 Bus Operations Without Cycle Stealing
Содержание TMPR7901
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