S2-LP datasheet(51/90 Pages) STMICROELECTRONICS

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S2-LP

Packet handler engine

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Packet handler engine

The S2-LP offers a highly flexible and fully programmable packet handler (framer and de-

framer) that build the packet according to the user configuration settings. The packet types

are available: BASIC format, STack format in which auto acknowledgment and auto

retransmission is used, 802.15.4g packet format and UART over the air packet format.

WMBUS format is supported but it can be obtained using the proper features combination.

The RX packet handler is in charge of treating the raw bits produced by the demodulator.

The main functions of the RX packet handler are:



Detect a valid preamble



Detect a valid synchronization word and start-of-frame



Extract all packet fields according to the selected packet format



Perform error correction and interleaving



Calculate the local CRC and compare to the received one

The device supports 4 different packet formats. The current packet format is set by the

PCK_FRMT field of the PCKTCTRL3 register.

In particular:



0: Basic packet format



1: 802.15.4g packet format



2: UART over the air packet format



3: STack packet format

7.1

BASIC packet format

The packet format BASIC is selected by writing 0b in the register PCK_FRMT. The packet

frame is as follows.

Table 48: BASIC packet format

Preamble

Sync

Length

Address

Payload

CRC

Postamble

0:2046 bits

0:32 bits

0:2 bytes

0:1 bytes

0:65535 bytes

0:4 bytes

0:510 bits



Preamble

: each preamble is a pair of ‘01’ or ‘10’ from 0 pair to 2046 pairs,

programmed by the register PREAMBLE_LENGTH. The binary sequences transmitted

in the various modulation modes are summarized in the following table (leftmost bit is

transmitted first).

Table 49: Preamble field selection

PREAMBLE_SEL

2(G)FSK or OOK/ASK

4(G)FSK

0101

0111

1010

0010

1100

1101

0011

1000



Sync: the pattern that identify the start of the frame can be configured in value with a

programmable length from 0 to 32 bits, in steps of 1-bit length. The setting is done by

the register SYNC_LENGTH. The S2LP supports dual synchronization with a either a

primary or a secondary synchronization word. The binary content of the primary SYNC

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