Final answer:
UART uses the Receive Data Ready (RDR) flag, typically in the UART status register, to signal an interrupt when the receive buffer has data. The flag notifies the processor to read the data, and its exact name or location varies by hardware. For precise implementation, referring to the hardware documentation or datasheet is necessary.
Step-by-step explanation:
The Universal Asynchronous Receiver Transmitter (UART) uses specific bits in certain registers to signal an interrupt when data is received in the receive buffer. The specific bit is usually found within the UART status register. For many UART controllers, this is typically the Receive Data Ready (RDR) flag. When this flag is set it indicates that there is data in the receive buffer that has not been read by the host processor. This flag can generate an interrupt to notify the processor that there is data waiting to be processed.
In addition to the RDR flag, there are other flags that indicate different types of receive buffer events, such as framing errors, parity errors, and buffer overruns, which can also generate interrupts. However, these are related to error handling and not the simple indication of available data to read.
The exact name or location of the flag can vary slightly depending on the manufacturer of the microcontroller or the specific UART implementation. To handle this interrupt correctly, one must consult the specific hardware documentation or datasheet for the microcontroller in use.