Product manual

XStream‐PKG‐R™RS‐232/485RFModem–ProductManualv5.x00[2006.02.24]
©2006MaxStream,Inc.Confidential&Proprietary   15
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RF Data Packet
Figure3.4. DataTransmissionSequenceÆ
The RF packet is the sequence of data used for communicating information between MaxStream
* When streaming multiple RF packets, the RF Initializer is only sent in front of the first packet.
RF Initializer
is sent each time a new connection sequence begins. The RF initializer contains
n the
Header
er contains network addressing information that filters incoming RF data. The receiving
CRC (Cyclic Redundancy Check)
uilt-in error checking, a 16-bit CRC (Cyclic Redundancy
e
Modems. An RF Packet consists of an RF Initializer and RF Data.
Figure3.5. RFDataPacketComponents
An RF initializer
channel information that notifies receiving modems of information such as the hopping pattern
used by the transmitting modem. The first transmission always sends an RF initializer.
An RF initializer can be of various lengths depending on the amount of time determined to be
required to prepare a receiving modem. For example, a wake-up initializer is a type of RF
initializer used to wake remote modems from Sleep Mode (Refer to the FH, LH, HT and SM
Commands for more information). The length of the wake-up initializer should be longer tha
length of time remote modems are in cyclic sleep.
The head
modem checks for a matching Hopping Channel (HP parameter), Vendor Identification Number
(ID parameter) and Destination Address (DT parameter). Data that does not pass through all
three network filter layers is discarded.
To verify data integrity and provide b
Check) is computed for the transmitted data and attached to the end of each RF packet. On th
receiving end, the receiving modem computes the CRC on all incoming RF data. Received data
that has an invalid CRC is discarded [Refer to the Receive Mode section, next page].