UART/Autobaud Functional Description
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UART Devices
12.5.5.2 DMA Transfers
Figure 12–11 shows DMA operation at receive; Figure 12–12 shows DMA
operation at transmit.
Figure 12–11.
Receive FIFO DMA Request Generation
Threshold reads
From system DMA
Programmable threshold
Receive FIFO level
Zero byte
time
DMA request
time
DMA request
active low
In receive mode, a DMA request is generated as soon as receive FIFO reach-
es its threshold. This request is deasserted when the number of bytes defined
by the threshold level has been read by the system DMA.
Figure 12–12. Transmit FIFO DMA Request Generation
Programmable threshold
Transmit FIFO level
Zero byte
time
DMA request
time
DMA request
Transmit FIFO level
Full level
active low
Threshold writes
from system DMA
Number
of spaces