L9662 datasheet(61/80 Pages) STMICROELECTRONICS

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L9662

Functional description

Protocol A

The data received from satellite receiver block has to be decoded in the digital block. The

data is received LSB first. The protocol format is defined below for the 4 different message

lengths.

Figure 16. Satellite protocol-A

The default for the device is to perform CRC decoding on all messages. The device has the

option not to perform the CRC decoding and pass the satellite message, excluding the 2

start bits, over the MISO. CRC decoding can be disabled/enabled by writing to the

appropriate bit in the CCR register.

For the CRC mode the error detection code used for processing the message is based on

the polynomial x3 + x1 + x0. If the device is in CRC mode it will process all incoming

messages and report an error via SPI2 in case of a CRC mismatch. The CRC is performed

after a complete message is received and, in case of CRC error, the device sets a fault code

in the SR word.

The message data sent over SPI2 is MSB first.

Protocol B: generic variable length protocol

The data received from satellite receiver block has to be decoded in the digital block. The

data is received LSB first. The protocol format is defined below for the 4 different message

lengths.

Figure 17. Generic satellite protocol

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