LRI64 datasheet(19/52 Pages) STMICROELECTRONICS

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LRI64

LRI64 protocol description

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LRI64 protocol description

The Transmission protocol defines the mechanism to exchange instructions and data

between the VCD and the LRI64, in each direction. Based on “VCD talks first”, the LRI64

does not start transmitting unless it has received and properly decoded an instruction sent

by the VCD.

The protocol is based on an exchange of:

●

a Request from the VCD to the LRI64

●

a Response from the LRI64 to the VCD

Each Request and each Response are contained in a Frame. The frame delimiters (SOF,

EOF) are described in the previous paragraphs.

Each Request (Figure 16) consists of:

●

Request SOF (Figure 7)

●

Request Flags (Table 3 to Table 5)

●

Command Code

●

Parameters (depending on the Command)

●

Application Data

●

2-byte CRC (Figure 15)

●

Request EOF (Figure 8)

Each Response (Figure 17) consists of:

●

Response SOF (Figure 11)

●

Response Flags (Table 6)

●

Parameters (depending on the Command)

●

Application Data

●

2-byte CRC (Figure 15)

●

Response EOF (Figure 12)

The number of bits transmitted in a frame is a multiple of eight, and thus always an integer

number of bytes.

Single-byte fields are transmitted Least Significant Bit first.

Multiple-byte fields are transmitted Least Significant Byte first, with each byte transmitted

Least Significant Bit first.

The setting of the flags indicates the presence of any optional fields. When the flag is set, 1,

the field is present. When the flag is reset, 0, the field is absent.

Figure 16.

VCD request frame format

AI09727

Request

SOF

Request

Flags

Command

Code

Parameters

Data

2-Byte

CRC

Request

EOF

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