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Figure 2–2. Display DMA Event Generation Flow Diagram
Start of field
FIFO empty
Generate DMA event,
new events disabled
Pending
DMA begun ?
No
FIFO
underrun ?
No
Yes
Underrun error
SPRU629
Display data, no DMA
pending
No
FIFO space
threshold
?
Yes
Yes
Event counter
EOF
expired ?
No
Generate DMA event
Display data, DMA
pending, new events
disabled
Pending DMA
begun ?
Yes
Yes
Display data, DMA
active, new events
enabled
FIFO space
2x threshold
?
Yes
Event counter
expired ?
No
Generate DMA
request
Display Data, DMA active,
and DMA pending
Yes
DMA complete
?
EOF
Display data
ield complete
F
?
No
No
FIFO underrun
?
Yes
Underrun error
No
No
Yes
FIFO underrun
?
Yes
No
No
DMA complete
?
Yes
EOF
No
No
Yes
FIFO underrun
?
Video Port
DMA Operation
Yes
End of field
Underrun error
No
FIFO underrun
?
Yes
Underrun error
Underrun error
2-9
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