UART/Autobaud Functional Description
12-41
UART Devices
Figure 12–9. Receive FIFO IT Request Generation
Programmable FIFO threshold
Receive FIFO Level
Zero byte
time
Interrupt request
time
Interrupt request active low
Programmable flow control threshold
Host acknowledged IT request
and transferred enough bytes to
recover FIFO level below
threshold
In receive, no interrupt is generated until receive FIFO reaches its threshold.
A low interrupt can only be deasserted when the host (MPU or DSP) has
handled enough bytes to make the FIFO level below threshold. Notice that flow
control threshold is set at a higher value than FIFO threshold.
Figure 12–10. Transmit FIFO IT Request Generation
Number
of
spaces
Programmable FIFO threshold
Transmit FIFO level
Zero byte
time
Interrupt request
ti
Interrupt request
active low
Full level
In transmit mode, an interrupt request is automatically asserted when the FIFO
is empty. This request is deasserted when the FIFO crosses the threshold
level. The interrupt line is deasserted until a sufficient number of elements
have been transmitted to go below FIFO threshold.
