UART/IrDA Functional Description
12-90
The RX_FIFO_STS bit (LSR[7]) generates the interrupt for the receiver line
status interrupt.
For the XOFF interrupt, if a XOFF flow character detection causes the inter-
rupt, the interrupt is cleared by a XON flow character detection. If special char-
acter detection causes the interrupt, the interrupt is cleared by a read of the
IIR.
12.9.3.2
Interrupts in SIR Mode
In the IrDA modes there are eight possible interrupts. The UART_nIRQ output
is activated when any of the eight interrupts is generated (there is no priority).
Table 12–89 summarizes the interrupt control functions in SIR mode.
Table 12–89. Generic Interrupt Functions in SIR Mode
IIR Bit No.
Interrupt Type
Interrupt Source
Interrupt Reset Method
7
Received EOF
Received end-of-frame
Read IIR
6
Receiver line
status interrupt
CRC, ABORT or frame-length
error is written into STATUS FIFO.
Read STATUS FIFO.
Read until empty—maximum eight
reads required.
5
TX underrun
THR empty before EOF sent
Read RESUME register
4
Status FIFO
interrupt
Status FIFO triggers level reached
Read STATUS FIFO.
3
RX overrun
Write to RHR when RX FIFO full.
Read RESUME register
2
Last byte in RX
FIFO
Last byte of frame in RX FIFO
Read IIR
1
THR interrupt
TFE (THR empty)
(FIFO disable)
TX FIFO below trigger level (FIFO
enable)
Write to THR until interrupt condition
disappears.
0
RHR interrupt
DRDY (data ready)
(FIFO disable)
RX FIFO above trigger level
(FIFO enable)
Read RHR until interrupt condition
disappears.