16.3 Function codes (FC)
The codes used are listed and explained in the following table:
FC [Dec] Meaning
1 Bitwise (reverse) reading of control information (one or more bits)
2 Bitwise reading of status information (one or more bits)
3 Wordwise (reverse) reading of nominal, measured and LONG values and parameters (one or more words)
4 Wordwise reading of status information (one or more words)
5 Bitwise resetting of control information (always one bit)
6 Wordwise writing of control bits or set-point values (always one data word)
8 Diagnosis (only subcode 0 and 1)
15 Bitwise writing of control information (one or more bits)
16 Wordwise writing of commands (one or more data words)
23 Wordwise reading and writing of several data words
This function code can be used everywhere FC3 or FC16 are possible.
16.4 Securing transmission
The characters are set by a parity bit, the telegrams are secured by a checksum (CRC16)
(see MODBUS specifications).
The MODBUS specifications determine the response to a transmission error (see 2-1
EXCEPTION RESPONSE).
Modbus 16.4 Securing transmission
INTECONT® Satus Operating Manual BV-H2346GB / 0833 79
© Schenck Process
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