S2-LPS datasheet(38/73 Pages) STMICROELECTRONICS

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Packet handler engine

The S2-LPS 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, 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

•

Calculate the local CRC and compare to the received one

The device supports 2 different packet formats. The current packet format is set by the PCK_FRMT field of the

PCKTCTRL3 register.

In particular:

•

0: Basic packet format

•

2: UART over the air packet format

6.1

BASIC packet format

The packet format BASIC is selected by writing 0b in the register PCK_FRMT. The packet frame is as follows:

Table 44. 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 1023 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 45. Preamble field selection

PREAMBLE_SEL

2(G)FSK or OOK/ASK

0101

1010

1100

0011

S2-LPS

Packet handler engine

DS13831 - Rev 1

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