Wizfi250 (UART1) has hardware flow control. User can enable or disable it. Moreover has pins RTS and CTS to carry hardware flow control. But the specification are say “UART1_RTS I/O” and “UART1_CTS I/O”. This means does not specified which one is output of wiz250, and which one is input of them. According my research CTS is out of wiz250, RTS is input of wiz250, but I’m not sure.
Function of this flow control also not specified. It can be control traffic from host to wiz250, or control traffic from wiz250 to host or can be bidirectional. The direction of the pins is imply it is control traffic from host to wiz250, but I’m not sure.