7556 - How to determine UART pin direction of the on-chip FTDI for Lattice Boards?
Lattice boards use the FTDI chip for onboard debugging and programming.
One of the interfaces that can be used is the UART port.
To easily identify FPGA port assignments for UART, users can refer below information.
TXD_UART (BDBUS0) is an output/transmitter pin on the FTDI side; therefore, at the FPGA, the pin configuration must be INPUT.
while
RXD_UART (BDBUS1) is an input/receiver pin on the FTDI side; therefore, at the FPGA, the pin configuration must be OUTPUT.