Flow Control
Flow Control
Flow control is the process of adjusting the flow of data from one device to another to ensure that the receiving device can handle all of the incoming data. Flow control becomes an important factor when one of the devices is capable of transmitting data at a rate faster than the other can receive it. There are two basic types of flow control, Hardware and Software.
Hardware Flow Control
Hardware flow control uses dedicated signal lines to dictate transmission of data. The options that allow you to select which pair of lines to use for this type of flow control are:
∙RTS/CTS = Request To Send/Clear To Send
∙DTR/DSR = Data Terminal Ready/Data Set Ready
NOTE |
The Windows flow control setting, “Hardware,” uses the RTS/CTS pair of flow control lines.
Software Flow Control
Software flow control uses two special characters, called “Xon” and “Xoff”, which are embedded in the data to turn on or off the transmission of data from the source to receiver.
In the incoming direction, flow control prevents the Ethernet Adapter from sending data when the computer is not ready to accept it. With incoming flow control on, the Ethernet Adapter will interpret Xon/Xoff characters in the data stream entering the serial port of the Ethernet Adapter as flow control signals. The Xon/Xoff characters are not considered data and therefore are absorbed by the Ethernet Adapter.
The outgoing software flow control option specifies the generation of Xon/Xoff flow control characters by the Ethernet Adapter. The control characters are sent out the serial port of the Ethernet Adapter and instruct the computer to start or stop sending data. This option is used to prevent the computer from sending data when the Ethernet Adapter is not ready to accept it.
Software flow control can have both incoming and outgoing mechanisms running simultaneously, individually, or not at all (as is the default).
General Serial Configuration
