Arasan 16550D High Speed UART IP core is a 16550-compliant Universal Asynchronous Receiver/Transmitter (UART) with FIFO or expanded FIFO. The UART performs serial to parallel conversion of data ...

The only other two signals connected are rx_byte — you can guess what that is — and isrx which goes high when something has come in on the serial port. The signals UART_RXD and UART_TXD now ...