To enable or disable hardware and software flow control, use the flow-control command in Serial Interface Configuration Mode. Flow control provides extra signaling to inform the transmitter that it should stop (pause) or start (resume) the transmission.
There is a hardware and software flow control.
For RS-232, the hardware method uses the RTS / CTS outputs. If the transmitter is ready to send data, then it sets the signal on the RTS line. If the receiver is ready to receive data, it sets the signal on the CTS line. If one of the signals is not set, no data transfer will occur.
The software method uses the Xon and Xoff characters (in the ASCII characters set: Xon = 17, Xoff = 19) which are transmitted using the same TXD / RXD communication lines as the main data instead of the pins. If the data cannot be received, the receiver transmits the Xoff symbol. To resume data transmission, the Xon symbol is sent.
| Parameter | Type | Description |
|---|---|---|
hardware
|
Enter this option to enable hardware flow control. | |
none
|
Enter this option for no flow control. | |
software
|
Enter this option to enable software flow control. |
Serial Interface Configuration Mode
iS5Comm(config)# configure terminal
iS5Comm(config)# interface serial 0/9
iS5Comm(config-serial-if)# flow-control hardware
iS5Comm(config-serial-if)# flow-control software
iS5Comm(config-serial-if)# flow-control none