An RX idle condition is detected when the receiver line (RX) is high for a time that equals 4x the programmed word length + 12 bits or manually configured amount of baud clocks, if a value other zero is set in the timeout register. RX is sampled midway through each bit.
For sleep mode, the counter is reset when there is activity on RX.
There are two modes of operation:
- In default operation on the UART_EFR2[6]
TIMEOUT_BEHAVE is set to 0. For the time-out interrupt, the counter counts only
when there is data in the RX FIFO, and the count is reset when there is activity
on RX or when the UART_RHR register is read.
- Optionally, for choose to enable the timeout
counter even if no character has been received by setting UART_EFR2[6]
TIMEOUT_BEHAVE bit. This will generate periodic interrupts if the RX line
remains idle. In this mode the counter will auto-reset when a timeout has been
reached. Reading the UART_IIR_UART will clear the interrupt, but not the
counter.