XBP24-PKI-001-RA Digi International/Maxstream, XBP24-PKI-001-RA Datasheet - Page 18

• Manufacturer Part Number: XBP24-PKI-001-RA
• Description: MODULE 802.15.4 RS-232 ANT
• Manufacturer: Digi International/Maxstream
• Series: XBEE-PRO™r

Specifications of XBP24-PKI-001-RA

• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: 802.15.4
• Applications: Home/Building Automation, Industrial Control, ZigBee™
• Power - Output: 0dBm
• Sensitivity: -92dBm
• Voltage - Supply: 2.8 V ~ 3.4 V
• Current - Receiving: 55mA
• Data Interface: Connector, Female DB-9
• Antenna Connector: RP-SMA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: Module
• Memory Size: -
• Current - Transmitting: -
• Other names: Q3255595

© 2008 Digi International, Inc.
XBee‐PRO PKG‐R® RS‐232 RF Modem – 802.15.4 ‐ Product Manual v1.xAx
CCA (Clear Channel Assessment)
Acknowledgement
Direct Transmission
A NonBeaconing Coordinator can be configured to use only Direct Transmission by setting the SP
(Cyclic Sleep Period) parameter to “0”. Also, a NonBeaconing Coordinator using indirect
transmissions will revert to direct transmission if it knows the destination modem is awake.
To enable this behavior, the ST (Time before Sleep) value of the Coordinator must be set to match
the ST value of the End Device. Once the End Device either transmits data to the Coordinator or
polls the Coordinator for data, the Coordinator will use direct transmission for all subsequent data
transmissions to that modem address until ST time (or number of beacons) occurs with no activity
(at which point it will revert to using indirect transmissions for that modem address). “No activity”
means no transmission or reception of messages with a specific address. Global messages will not
reset the ST timer.
Indirect Transmission
To configure Indirect Transmissions in a PAN (Personal Area Network), the SP (Cyclic Sleep Period)
parameter value on the Coordinator must be set to match the longest sleep value of any End
Device. The SP parameter represents time in NonBeacon systems and beacons in Beacon-enabled
systems. The sleep period value on the Coordinator determines how long (time or number of
beacons) the Coordinator will retain an indirect message before discarding it.
In NonBeacon networks, an End Device must poll the Coordinator once it wakes from Sleep to
determine if the Coordinator has an indirect message for it. For Cyclic Sleep Modes, this is done
automatically every time the modem wakes (after SP time). For Pin Sleep Modes, the A1 (End
Device Association) parameter value must be set to enable Coordinator polling on pin wake-up.
Alternatively, an End Device can use the FP (Force Poll) command to poll the Coordinator as
needed.
Prior to transmitting a packet, a CCA (Clear Channel Assessment) is performed on the channel to
determine if the channel is available for transmission. The detected energy on the channel is
compared with the CA (Clear Channel Assessment) parameter value. If the detected energy
exceeds the CA parameter value, the packet is not transmitted.
Also, a delay is inserted before a transmission takes place. This delay is settable using the RN
(Backoff Exponent) parameter. If RN is set to “0”, then there is no delay before the first CCA is
performed. The RN parameter value is the equivalent of the “minBE” parameter in the 802.15.4
specification. The transmit sequence follows the 802.15.4 specification.
By default, the MM (MAC Mode) parameter = 0. On a CCA failure, the modem will attempt to re-
send the packet up to two additional times.
When in Unicast packets with RR (Retries) = 0, the modem will execute two CCA retries.
Broadcast packets always get two CCA retries.
If the transmission is not a broadcast message, the modem will expect to receive an
acknowledgement from the destination node. If an acknowledgement is not received, the packet
will be resent up to 3 more times. If the acknowledgement is not received after all transmissions,
an ACK failure is recorded.
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