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7.2.2 Agreement
Frame
start
Arbitratio
n segment
Control
segment
Data segment
CRC
segment
ACK
segment
Frame end
When the data frame reaches the terminal device, it enters the addressable device through a simple
“port”. The device removes the envelope "envelope" (data header) of the data frame and reads the
data. If there is no data, the task requested by the data is executed. Then, if the returned data
is available, the data generated by itself is packed in the “envelope”, and the data frames are
returned to the sender.
7.2.2.1 Data frame format
7.2.2.2 Frame start
Represent a segment that a frame starts, with dominant of a bit.
The bus wire has two kinds of electrical levels which are “dominant” and “recessive”. When
executing the line “and” on the bus wire, the logical value of the dominant level is “0”, and
the logical value of the recessive level is “0”. “Dominant” has the meaning of “priority”,
as long as there is a unit outputting dominant level, the bus wire is the dominant level.
“Recessive” has the meaning of “containment”, only when the output of all units is the recessive
level, the bus wire is
the
recessive level.
7.2.2.3 Arbitration segment
The segment representing the data precedence.
The data frames stipulated in the CAN communication protocol have two formats, which are standard
format and extended format, and the arbitration segments of the two formats are different. Acrel
AIM-M300/SG insulation monitors uses the standard format, of which the arbitration segment has 11
bits. It is sent in turn from ID28 to ID18, and prohibits the high 7 bits are all recessive.
7.2.2.4 Control segment
The control segment consists of 6 bits, representing the number of bytes in the data segment,
and the composition of the standard format and the extended format is different.
The Acrel AIM-M300(or AIM-M300/SG) insulation monitor uses the standard format, consisting of
a IDE bit, a reserved bit, and 4 bits of data-length-code DLC.
Note that the bytes of data must be 0-8 bytes, but the receiver does not consider the case of
9-15 as an error.
7.2.2.5 Data segment
Data segment can contain data of 0-8 bytes, starting with the MSB (Most significant bit).
7.2.2.6 CRC 段
7.2.2.6 CRC segment
