Reference Manual

2. Basic Radio Programming and Setup
FGR3
User-Reference Manual
LUM0110AA Rev Jan-2019 Page 58 of 143 Copyright © 2019FreeWave
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RTS to CTS
Setting Description
Description: Use this option to set the RTS line on the Master radio to control the CTS line of
the Slave.
With RTS to CTS enabled:
l In MultiPoint networks, the Master RTS line controls all Slave's CTS lines.
l The CTS line stops functioning as flow control.
l The Master senses the RTS line prior to all scheduled packet transmissions.
l If the state has changed, the Master then transmits a message to the Slave
with the new status. This transmission occurs regardless of data being
sent.
l If data is ready to be sent, the RTS status message is sent in addition to the
data.
l In Point-to-Point mode, the Master continues sending the new status message
until it receives an acknowledgment from the Slave.
l In MultiPoint mode, the Master repeats the message the number of times
equal to the Master Packet Repeat value in the MultiPoint Parameters tab.
l Master transmit times are completely asynchronous to the occurrence of any
change of the RTS line; the latency time from RTS to CTS is variable.
l The Max and Min Packet Size parameters determine this duration.
l Setting both parameters to their maximum value of 9 produces a maximum
latency time of approximately 21ms, given no Repeaters in the network.
l At the minimum settings for Max and Min Packet Size (0), the time is
approximately 5.9ms.
l This latency can increase significantly if packets are lost between the Master
and Slave.
l In Point-to-MultiPoint mode, no absolute guarantee is made that the state
change is communicated to all Slaves.
l In MultiPoint networks with Repeaters present, the latency is cumulative for
each serial Repeater.
Example: If the latency between the Master and the first Repeater is
15ms, and two serial Repeaters are present, the total latency is 45ms.
(M—R1 (15ms) + R1—R2 (15ms) + R2—S (15ms) = 45ms).
Important!: The RTS to CTS feature does NOT function in Point-to-Point
networks that contain a Repeater.
If this feature is needed in such network, the mode should be changed to
Point-to-MultiPoint.
l If DTR Connect on the Tool Suite MultiPoint Parameters tab is enabled
and set to 2, the RTS to CTS feature does not work.