SPIRIT1 datasheet(56/94 Pages) STMICROELECTRONICS

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Transmission and reception

SPIRIT1

56/94

Doc ID 022758 Rev 3

Example 1

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If the variable payload length is from 0 to 31 bytes, then LEN_WIDTH = 5

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If the variable payload length is from 0 to 255 bytes, then LEN_WIDTH = 8

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If the variable payload length is from 0 to 65535 bytes, then LEN_WIDTH = 16.

CRC (programmable/optional field): There are different polynomials CRC: 8 bits, 16 bits (2

polynomials are available) and 24 bits. When CRC automatic filtering is enabled, the

received packet is discarded automatically when CRC check fails.

9.7.2

Wireless M-Bus packet (W M-BUS, EN13757-4)

The WM-BUS packet structure is shown in the figure below (refer to EN13757 for details

about sub-mode specific radio setting).

The preamble consists of a number of chip sequences '01' whose length depends on the

chosen sub-mode according to EN13757-4. The length can be programmed using the

MBUS_PRMBL_CTRL, from a minimum to a maximum dictated from the standard

specification.

1st block, 2nd block, and optional blocks: can be defined by the user. The packet handler

engine uses the Manchester or the “3 out of 6” encoding for all the blocks according to the

defined sub-mode.

The postamble consists of a number of chip sequences '01' whose length depends on the

chosen sub-mode according to EN13757-4. The length can be programmed using the

MBUS_PSTMBL_CTRL, from a minimum to a maximum dictated from the standard

specification.

Bytes nx(01)

nx(01)

Preamble

Sync

1st block

2nd block

Opt. blocks

Postamble

Manchester or 3 out of 6 encoding

SPIRIT1 Datasheet(PDF) 56 Page - STMicroelectronics