ATI Q46 Modbus Communications Manual
4
O&M Manual
Rev-D (2/16)
The data field can be nonexistent (of zero length) in certain kinds of messages. For example, in a
request from a master device for a slave to respond with its communications event log (function
code 0B hexadecimal), the slave does not require any additional information. The function code
alone specifies the action.
Messages are terminated with a 16-bit CRC value that is computed from all of the bytes of the
message. The two byte CRC is superior to just simple checksums because it can help reject
more types of errors.
Figure 1 - Modbus Terminal Connections
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