A transmission frame can be terminated in two ways:
- Frame-length method: Set the UART3.UART_MDR1[7] FRAME_END_MODE bit to 0. The MPU writes the value of the frame length to the UART3.UART_TXFLH and UART3.UART_TXFLL registers. The device automatically attaches end flags to the frame when the number of bytes transmitted equals the value of the frame length.
- Set-EOT bit method: Set the FRAME_END_MODE bit to 1. The MPU writes 1 to the UART3.UART_ACREG[0] EOT bit just before it writes the last byte to the TX FIFO. When the MPU writes the last byte to the TX FIFO, the device internally sets the tag bit for that character in the TX FIFO. As the TX state-machine reads data from the TX FIFO, it uses this tag-bit information to attach end flags and correctly terminate the frame.