SX1210 SEMTECH [Semtech Corporation], SX1210 Datasheet - Page 42

• Manufacturer Part Number: SX1210
• Description: Ultra-Low Power Integrated UHF Receiver
• Manufacturer: SEMTECH [Semtech Corporation]

The length stored in this register relates only to the payload which includes the message and the optional address
byte. In this mode, the payload must contain at least one byte, i.e. address or message byte.
An illustration of a fixed length packet is shown in Figure 34. It contains the following fields:
This mode is necessary in applications where the length of the packet is not known in advance and can vary over
time. It is then necessary for the transmitter to send the length information together with each packet in order for
the receiver to operate properly.
In this mode the length of the payload, indicated by the length byte in Figure 35, is given by the first byte of the
FIFO and is limited only by the size (width of 8bits) of the FIFO selected. Note that the length byte itself is not
included in its calculation. In this mode, the payload must contain at least 2 bytes, i.e. length + address or message
byte.
An illustration of a variable length packet is shown in Figure 35. It contains the following fields:
Rev 2– Sept 8
ADVANCED COMMUNICATIONS & SENSING
Preamble (1010...).
Sync word (Network ID).
Optional Address byte (Node ID).
Message data.
Optional 2-bytes CRC checksum.
Preamble (1010...).
Sync word (Network ID).
Length byte
Optional Address byte (Node ID).
Message data.
Optional 2-bytes CRC checksum.
th
, 2008
5.5.2.2. Variable Length Packet Format
1 to 4 bytes
Preamble
Optional User provided fields which are part of the payload
Message part of the payload
Fields processed and removed by the packet handler
1 to 4 bytes
Sync Word
Figure 34: Fixed Length Packet Format
Address
byte
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CRC checksum calculation
Optional DC free data decoding
Payload/FIFO
0 to (FIFO size) bytes
Message
2-bytes
CRC
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SX1210