Page 106 SMV800 Modbus User's Guide Revision 1.0
3.2.3. Baud Rate (Software Configurable)
Default baud rate: 9600
Available baud rate: 1200, 2400, 4800, 9600, 19200
Make sure the RS-485 network is only terminated twice on the entire bus. Best practice
would suggest this be done once on each end. Termination at multiple point on the bus will
hamper communication.
The format for both query and response frames is as follows:
For communication to specific SMV800 Modbus, the address field contains the slave’s
polling address. The function field contains a function code. Which indicates the read, write
or diagnostic command to be performed as part of query. When the SMV800 modbus
device responds to a query, the function field will either verify the device’s response
provide an exception that explains any errors encountered while processing the command.
Table 3-1 provides an overview of these response codes. When transmitters receive a
query, it will not respond until the command has been completed. No subsequent
commands will be processed until the first command is finish.
Table 3-1: Exception Response Codes
The slave is engaged in processing a long
duration command. The host should retransmit
the message later when the slave is free.
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