UARTE can generate an event after a programmable timeout.
If enabled with the FRAMETIMEOUT field in register CONFIG, a counter starts at the start flag, and counts the number of bit periods given in register FRAMETIMEOUT. The period time of the counter is equal to the period of one bit on the UART TX line given by the BAUDRATE register. When the timeout expires, the event EVENTS_FRAMETIMEOUT is generated. The STOP task also stops the timeout counter. UARTE reception can be stopped on timeout by setting the short from the FRAMETIMEOUT event to the DMA.RX.STOP task in register SHORTS.
This feature can be used to support variable length UART transmission with no end of transmission tag. After the last UART frames are received within the configured timeout, an interrupt is generated and the data can be processed.
The following figure shows an example where the UART receives a transmission that times out after byte 12.
The minimum value of the FRAMETIMEOUT register must be set to a value larger than the configured UART frame length.