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CL4490 User’s Manual
1.6 Hardware Flow Control
Flow control refers to the control of data flow between the host and the CL4490. It is the
method used to handle data in the transmit/receive buffer of the CL4490 interface, and
determines how data flow between the host and the CL4490 is throttled. Often in serial
communication, one device is capable of sending data much faster than the other can
receive. Flow control allows the slower device to tell the faster device to pause and resume
data transmission. (Flow control CTS and RTS are used by the CL4490 and its Host, locally
– NOT over the air. Therefore, one CL4490 cannot tell the other to slow down or speed up
as is mentioned above in the paragraph.)
When the RTS Enable option is selected on the Configuration Utility, the transceivers use
hardware flow control to regulate data flow. While using hardware flow control, the
transceiver that is ready to receive data sends a Clear To Send signal to its host (or the
device it is connected to). On the other hand, when a transceiver has something it wants to
send to its host, it checks the state of Ready To Send and if it is logic low, will send data to its
host. If RTS is logic high, it will not send data to its host. These signals are sent apart from
the data itself on separate wires. Note: CTS is always enabled by default. RS-485
Interface does not support Hardware flow control.
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