LRI512 Просмотр технического описания (PDF) - STMicroelectronics
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LRI512
STMicroelectronics
LRI512 Datasheet PDF : 54 Pages
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LRI512
LRI512 PROTOCOL DESCRIPTION
The Transmission protocol defines the mecha-
nism to exchange instructions and data between
the VCD and the LRI512, in both directions.
It is based on the concept of “VCD talks first”.
This means that any LRI512 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 LRI512
– a Response from the LRI512 to the VCD
Each Request and each Response is contained in
a Frame. The frame delimiters (SOF, EOF) are de-
scribed in the previous paragraphs.
Each Request consists of
– Request SOF (see Figure 9 and Figure 10)
– Flags
– A Command Code
– Parameters, depending on the Command
– Application data
– 2-byte CRC
– Request EOF (see Figure 11)
Each Response consists of
– Answer SOF (see Figure 20 to Figure 23)
– Flags
– Parameters, depending on the Command
– Application data
– 2-byte CRC
– Answer EOF (see Figure 24 to Figure 27)
The protocol is bit-oriented. The number of bits
transmitted in a frame is a multiple of eight (8) –
that is, an integer number of bytes.
A single-byte field is transmitted Least Significant
Bit (LSBit) first.
A multiple-byte field is transmitted Least Signifi-
cant Byte (LSByte) first, each byte is transmitted
Least Significant Bit (LSBit) first.
The setting of the flags indicates the presence of
the optional fields. When the flag is set (to one),
the field is present. When the flag is reset (to zero),
the field is absent.
Table 7. VCD Request Frame Format
Request
SOF
Request Flags Command Code
Parameters
Data
2 Bytes
CRC
Request
EOF
Table 8. LRI512 Response Frame Format
Response
SOF
Response
Flags
Parameters
Data
2 Bytes
CRC
Response
EOF
Figure 29. LRI512 Protocol Timing
VCD
LRI512
Request Frame
(Table 7)
Response Frame
(Table 8)
Request Frame
(Table 7)
Response Frame
(Table 8)
Timing
t1
t2
t1
t2
AI06830
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