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CAN232 FD User Manual
accepted when the
mode
option under
command
settings in configuration is set to
one-shot
. In this mode,
no attempts to automatically retry on error will happen. This is used in time-triggered CAN protocols.
All message string characters are in upper case only. Lower case characters will be interpreted as a syntax
error and the message will be discarded.
Identifier and data fields are treated as base-16 digits (hexadecimal).
The syntax of both transmit and receive message strings are identical.
There are three types of message strings:
- Normal CAN messages
- Remote Transmission Request CAN messages (RTR)
- Report CAN error status messages (optional)
As per the CAN 2.0A/B specification, RTR messages do not contain data. To support RTR messages, the
syntax is modified to include an explicit single-digit length. The length field is treated as a base-10 digit and
must be a single digit between 0 and 8. The CAN FD specification does not support Remote frames.
3.1.1.1 Normal CAN Message
A normal CAN message consists of the identifier type (11-bit or 29-bit), identifier, CAN type, and data
bytes and is encoded as follows:
Normal CAN Message Syntax
: <S | X> <IDENTIFIER> <N | F | H> <DATA-0> <DATA-1> … <DATA-n> ;
The first character,‘:’, is for synchronization and allows the CAN232 FD parser to detect the beginning of a
command string.
The following character is either ‘S’ for standard 11-bit, or ‘X’ for extended 29-bit identifier type.
The ‘IDENTIFIER’ field consists of three or eight hexadecimal digits, indicating the value of the identifier.
Note that if a 29-bit value is entered and an 11-bit value was specified, the command will be treated as
invalid and ignored.
The character ‘N’ indicates that the message is a normal (non-RTR) CAN 2.0A/B transmission. The
character ‘F’ or ‘H’ indicates that the message is a normal CAN FD transmission without or with the higher
data baud rate switch (BRS) respectively.
Each ‘DATA-n’ field is a pair of hexadecimal digits defining the data byte to be sent. If no data is to be sent
(length = zero), then the data bytes are omitted. CAN FD messages can be up to 64 data bytes in length
where only lengths 0 – 8, 12, 16, 20, 24, 32, 48 and 64 are valid based on the standard.
Each data byte specified must be a hexadecimal pair in order to eliminate ambiguity.
The terminating character ‘;’ signals the end of the message.
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