Description: This determines the flow control protocol to be used, either no flow control, xon-xoff, rts-cts full duplex or rts-cts. Full duplex rts/cts uses the rts and cts lines as two independent signals. The DTE signals to the DCE that it is prepared to accept more data by asserting RTS, the DCE signals to the DTE that is is prepared to accept more data by asserting CTS. Half duplex rts/cts (the conventional way) uses CTS as a response to RTS, the DCE flow controls the DTE by only returning CTS is response to a RTS from the DTE when the DCE can accept more data. The DTE can flow control the DCE by raising RTS when it does not want to receive any more input and dropping it when it is ready to receive more.