Configuration and commands Network commands
XBee®-PRO 900HP/XSC RF Modules
213
After transmitting a packet, the transmitting device waits to receive an ACK from a receiving device. If
it does not receive the ACK in the time that RN specifies, it transmits the original packet again. The
transmitting device transmits the RF packet repeatedly until it receives an ACK or until it sends the
packet RR times.
Note You must have retries enabled for all modules in the network for retries to work.
Binary command
0x18 (24 decimal)
Parameter range
0 - 0xFF
Default
0 (disabled)
Bytes returned
1
SY (Time Before Initialization)
Keeps a communication channel open as long as the device transmits or receives before the active
connection expires. You can use this command to reduce latency in a query/response sequence and
set it 100 ms longer than the delay between transmissions. This command allows multiple Modules to
share a hopping channel for a given amount of time after receiving data.
By default, all packets include an RF initializer that contains channel information used to synchronize
any listening receivers to the transmitter’s hopping pattern. Once a new device comes within range, it
is able to instantly synchronize to the transmitter and start receiving data. If no new devices are
introduced into the system, the synchronization information becomes redundant once devices have
become synchronized.
The SY command allows the devices to remove this information from the RF Initializer after the initial
synchronization. For example, changing the SY Parameter to 0x14 (20 decimal) allows all devices to
remain in sync for 2 seconds after the last data packet was received. The device does not send
synchronization information unless transmission stops for more than 2 seconds. This command allows
significant savings in packet transmission time.
The SY command is not supported above a value of 5 when interfacing an XBee-PRO XSC S3B with a
9XStream.
We do not recommend this command for use in an interference-prone environment.
Interference can break up the session making the communications channel unavailable
until the SY time expires. If you set SY to zero, the channel session opens and closes with
each transmission, resulting in a more robust link with increased latency.
Binary command
0x17 (23 decimal)
Parameter range
0 – 0xFF [x 100 milliseconds]
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