Use UART_GetRxStatus() and test for a byte already received and read it with UART_ReadRxData().
Are you trying to test for the logic state of the pin itself ? Independent
of UART framing ?
If this is the case you could poll the pin using - CyPins_ReadPin(pinPC)
Use the existing UART example project and try to send 0x00 from hyperterminal or vice versa. It would definitely work.
His stated problem is "I want to read ZERO '0' on the UART receive pin.",
not how do I send and receive "0" as a character into the UART buffer.