GridConnect CAN232 FD, Руководство пользователя

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CAN232 FD User Manual 3-9
3. Operation
The following sections describe the operation of the CAN232 FD.
3.1 CAN Command Mode
In the command mode, the CAN232 FD is capable of sending and receiving arbitrary CAN messages via the
use of ASCII or Binary formatted message strings (Figure 3).
Figure 3
When the CAN232 FD receives a valid command message on the serial line, it converts it to a CAN
message and transmits it out over the CAN network.
Conversely, when a CAN message is received by the CAN232 FD, it converts it to a command message and
transmits it out of the serial port.
The CAN232 FD supports ten (10) CAN receive message filters each for standard IDs and Extended IDs
consisting of individual IDs, ID ranges or classic ID masks. By using the masks to specify which bits of an
identifier are to be compared to the filter value, the CAN232 FD is capable of selecting an arbitrary sub-set
of the total possible CAN messages and rejecting all others. Thus, only desired messages will be received
and the total required bandwidth of the serial link is kept to a minimum.
3.1.1 ASCII Message String Syntax
Message strings are formatted as human-readable ASCII sequences that are easy to enter and read. Each
message string is of variable length, depending on the number of data bytes included in the message.
In order to facilitate human CAN network monitoring, there is an option to append a CR/LF sequence to
each output ASCII message string. Doing so makes it much easier to watch the incoming messages on a
terminal where each message is on a separate line. See
Appending CR/LF To Received Command Strings
on page 3-12.
Messages starting with ‘|’ will generate a self-receive of the transmitted message. If the message is
transmitted on CAN successfully, it will be received back on the serial line as if it had been sent from some
other node.
Terminating with ‘!’ instead of ‘;’ indicates the intent is a one-shot transmit. This command option is
maintained in the firmware for backward compatibility with previous versions. A one-shot message is only