LRI64 datasheet(13/38 Pages) STMICROELECTRONICS

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LRI64

LRI64 PROTOCOL DESCRIPTION

The Transmission protocol defines the mecha-

nism to exchange instructions and data between

the VCD and the LRI64, in each direction. Based

on “VCD talks first”, the LRI64 does not start trans-

mitting unless it has received and properly decod-

ed 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 17.) consists of:

–

Request SOF (Figure 8.)

–

Request Flags (Table 3. to Table 5.)

–

Command Code

–

Parameters (depending on the Command)

–

Application Data

–

2-byte CRC (Figure 16.)

–

Request EOF (Figure 9.)

Each Response (Figure 18.) consists of:

–

Response SOF (Figure 12.)

–

Response Flags (Table 6.)

–

Parameters (depending on the Command)

–

Application Data

–

2-byte CRC (Figure 16.)

–

Response EOF (Figure 13.)

The number of bits transmitted in a frame is a mul-

tiple 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 Signifi-

cant 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 ab-

sent.

Figure 17. VCD Request Frame Format

Figure 18. LRI64 Response Frame Format

Figure 19. LRI64 Protocol Timing

AI09727

Request

SOF

Request

Flags

Command

Code

Parameters

Data

2-Byte

CRC

Request

EOF

AI09728

Response

SOF

Response

Flags

Parameters

Data

2-Byte

CRC

Response

EOF

AI06830B

VCD

Request Frame

VICC

Response Frame

Timing

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