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Post
by:
leaner
member
ID 15175
Date: 05/27/2007
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Help me, Giup em voi
Em dịch cái này mà không được, ai biết dịch giúp em với!!! cảm ơn!
[edit] Frames
A CAN network can be configured to work with two different message (or "frame") formats: the standard or base frame format (or CAN 2.0 A), and the extended frame format (or CAN 2.0 B). The only difference between the two formats is that the “CAN base frame” supports a length of 11 bits for the identifier, and the “CAN extended frame” supports a length of 29 bits for the identifier, made up of the 11-bit identifier (“base identifier”) and an 18-bit extension (“identifier extension”). The distinction between CAN base frame format and CAN extended frame format is made by using the IDE bit, which is transmitted as dominant in case of an 11-bit frame, and transmitted as recessive in case of a 29-bit frame. CAN controllers, which support extended frame format messages are also able to send and receive messages in CAN base frame format. All frames begin with a start-of-frame (SOF) bit that, obviously, denotes the start of the frame transmission.
CAN has four frame types:
Data frame: a frame containing node data for transmission
Remote frame: a frame requesting the transmission of a specific identifier
Error frame: a frame transmitted by any node detecting an error
Overload frame: a frame to inject a delay between data and/or remote frames
[edit] Data frame
The data frame is the only frame for actual data transmission. There are two message formats:
Base frame format: with 11 identifier bits
Extended frame format: with 29 identifier bits
The CAN standard requires the implementation must accept the base frame format and may accept the extended frame format, but must tolerate the extended frame format.
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