Rosemount 3095FB - Broadcast Mode and Address 0; Data Field; Error Check Field

Model 3095FB Multivariable Transmitter with Modbus Protocol
Modbus Protocol Guide
Page 7 of 79
In a response frame, the function field contains a function code verifying the device’s
response to the command. If the most significant bit in the function field is set, the data field
contains an exception response that explains any errors encountered while processing the
command (see Section 2.5) in the Modbus Protocol Guide.
2.2.3 Data Field
The data field contains information that is specific to each individual function. Section 2.4
gives the data field layout for each function.
2.2.4 Error Check Field
The error check field contains a 16 bit CRC checksum that is used to verify the integrity of
the message frame.
2.2.5 Broadcast mode and address 0
Any query message with a slave address of 0 is a broadcast message. Only Modbus function
codes that write to a register or coil are valid in a broadcast message. Address 0 is reserved
for broadcast messages and therefore is not a valid Modbus slave address.