SM1212E433 Semtech, SM1212E433 Datasheet - Page 50

• Manufacturer Part Number: SM1212E433
• Description: RF Module For SX1212
• Manufacturer: Semtech
• Series: -r
• Type: Transceiver, ISMr

Specifications of SM1212E433

• Frequency: 433MHz
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: SX1212E

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 43. 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 44, is given by the first byte of the
FIFO and is limited only by the width 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 44. It contains the following fields:
Rev 2 – June 18th, 2009
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.
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 added by the packet handler in Tx and processed and removed in Rx
1 to 4 bytes
Sync Word
Figure 43: Fixed Length Packet Format
Address
byte
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CRC checksum calculation
Optional DC free data coding
Payload/FIFO
0 to (FIFO size) bytes
Message
2-bytes
CRC
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