Lpc2000

I am working with a RS485 transceiver that echoes the transmitted data
back through the receive channel.  When I switch transmission
direction from receive to transmit I wish to ignore the incoming data
as it is just a copy of what is being set.  I can't disable the UART1
in the VIC as this would kill all UART operations.  So I am trying to
disable the RBR interrupt in the U1IER register.  The problem is that
when I do this it triggers an RDA interrupt immediatly.

What am I missing here?

Thanks

Rich