S2-LP datasheet(56/90 Pages) STMICROELECTRONICS

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Packet handler engine

S2-LP

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When this format is selected, a start bit and a stop bit can be programmed to be added to

each byte of the TX FIFO. Such start and stop bits are automatically removed from the

received payload before written to the RX FIFO. Start and stop bits are not added to the

SYNC word.

Also, the BYTE_SWAP bit can be set in order to send the FIFO bytes in LSbit first (default

is indeed MSbit first).

The actual binary value of the start and stop bit can be set through the START_BIT and the

STOP_BIT fields of the PCKTCTRL2 register.

7.5

Wireless MBUS packet (W-MBUS, EN13757-4)

The W-MBUS packet structure referred to EN13757 can be obtained through registers

setting programming the Basic packet to fit the specific sub-mode used.

Preamble

Sync

1st block

2nd block

Opt. blocks

Postamble

Preamble: the preamble is fully programmable to fit the W-MBUS protocol. The generic

setting is a pair of ‘01’ or ‘10’ from 1 pair to 1024 pairs (max 256 bytes).

Sync: the pattern that identify the start of the frame is fully programmable to fit the W-

MBUS protocol. The generic setting is in value with a programmable length from 1 bit to 64

bytes, in steps of 1-bit length.

Data blocks: the data coding can be fully programmed in NRZ, Manchester or 3-out-of-6.

Postamble

: The packet postamble allows inserting a certain number of ‘01’ bit pairs at the

end of the data packet. The number of postamble bit pairs can be set through the

MBUS_PSTMBL register depending on the chosen sub-mode according to the W-MBUS

protocol.

7.6

Payload transmission order

The bit order of the data from TX FIFO and written into the RX FIFO is controlled by the

BYTE_SWAP register. In particular, the transmission is MSB first if BYTE_SWAP = 0 and

LSB first if BYTE_SWAP = 1.

7.7

Automatic packet filtering

The receiver uses the following filtering criteria to reject the received packet. The automatic

filtering is supported in BASIC and STack packet format only.



CRC: the received packet is discarded if CRC check fails. Both transmitter and

receiver must be configured with same CRC polynomial.



Destination address vs my address: the received packet is discarded if the

destination address field received does not match the programmed my address of the

receiver.



Destination address vs. broadcast address: the received packet is discarded if the

destination address field received does not match the programmed broadcast address

of the receiver.



Destination address vs. multicast address: the received packet is discarded if the

destination address field received does not match the programmed multicast address

of the receiver.



Source address: the received packet is discarded if the source address received

does not match the programmed source address reference (a bit mask can be

included). Supported in STack packet format only.

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