Spread Spectrum Wireless Data Transceiver User Manual
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RTS
TO
CTS
Menu selection RTS to CTS in the Radio Parameters provides the option of allowing the RTS line on the
Master transceiver to control the CTS line of the Slave. This pass-through control can be enabled in both
Point-to-Point and Point-to-MultiPoint. In the latter, the Master RTS line will control all Slaves’ CTS lines.
When this mode is enabled, the CTS line ceases to function as flow control. Therefore, it is not
recommended to enable this feature when operating at RS-232 speeds above 38.4 kB.
To enable this mode, enter 7 in the Radio Parameters menu. An entry of 1 will enable the RTS-CTS
control, 0 will disable it.
Just prior to the time the Master is scheduled to transmit a packet, it will sense the state of the RTS line. If
the state has changed, the Master will then transmit a message to the Slave with the new status. This
transmission will occur regardless of data being sent. If data is present to be sent, the RTS status
message will be sent in addition to the data. In Point-to-Point mode the Master will continue sending the
new status message until it receives an acknowledgment from the Slave. In Point-to-MultiPoint mode, the
Master will repeat the message the number of times equal to the Master Packet Repeat number in the
MultiPoint Setup menu.
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. The maximum time, however, is determined by the frequency of
Master transmission times. The Maximum Packet Size and Minimum Packet Size parameters in the
Radio Parameter menu determine this frequency. Setting both parameters to their maximum of 9 and 9
will produce a maximum latency time of approximately 21 ms. At their minimum numbers the time will be
approximately 5.9 ms. Please note that this latency can increase significantly if packets are lost between
the Master and Slave. In Point-to-MultiPoint mode, there is no absolute guarantee that the state change
will be communicated to all Slaves in the unlikely event that all repeated packets from the Master do not
get through to all Slaves.
Notes:
The RTS to CTS mode does not function in Point-to-Point links which contain a Repeater. If this
feature is needed in a link with a Repeater, the network mode should be changed to Point-to-
MultiPoint.
If DTRConnect is enabled and set to 2, RTS to CTS mode will not work.
If the DTRConnect is enabled and set to 1, RTS to CTS mode takes precedence over the
functionality of the CTS line on the slave relating to the DTRConnect feature.
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R
ETRY
T
IME
O
UT
The Retry Time Out parameter in a Slave or Repeater will allow it to drop a connection to a Master or
Repeater in MultiPoint mode. The default setting is 255, meaning that if 1 packet in 255 from the Master
is sent successfully to the Slave or Repeater, it will maintain a link. The lowest setting is 8. This setting
will allow a Slave or Repeater to drop a connection if fewer than 1 of 8 packets send successfully.
The Retry Time Out parameter is useful when a MultiPoint system has a moving Master or Slaves. As the
link gets weaker, a lower setting will allow a transceiver to drop a link and search for a different
connection.
While intended primarily for MultiPoint systems, the Retry Time Out parameter may also be modified in
Point-to-Point systems. In Point-to-Point mode the Retry Time Out should not be set to a value of less
than 151.
LUM0002AD Version
6.1
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