Check every 200ms, if nothing is recieved on UART Rx, transmit something on UART Tx. This continues till we recieve something on Rx. And if valid data in UART Rx, dont send anything on UART Tx.
You'll need a 200ms timer and set a flag in the interrupt handler.
In the main infinite loop check for the flag set, act accordingly and reset the flag.
Seems to be quite straightforward. When you get stuck upload a workspace archive so we can have a look at.
Is there a reason why you use a PSoC1 and not a more modern PSoC 4 with debug capabilities as the CY8CKIT-043 ?