I've done the following:
UART_C2_REG[ RIE ] = 1 //Enable interrupt when S1[RDRF] is set.
UART_C2_REG[ TE ] = 1//Enable Transmitter
UART_C2_REG[ RE ] = 1 //Enable Receiver
UART_C5_REG[ RDMAS ] = 0 //Configure for interrupt, not DMA.
UART_RWFIFO_REG[ UART_RWFIFO_RXWATER ] = 1 //Set interrupt to occur after 1 byte is present in the buffer.
I'll spare you the rest of my configuration, but please know I have UART0 working with 100MHz clock and configured with 115200 baud rate.
I've also added the name of my interrupt function (UART__INTERRUPT__RX) at IRQ 45 (address 0x0000_00F4) of the Vector Table.
However, function UART__INTERRUPT__RX() is never entered when I send keypresses via HyperTerminal. I can see the data I transmit to HypterTerminal.
I thought I had everything correctly setup. What else do I need to configure to make this work?