Appendix B - Modbustcp Guide; Introduction; Modbus Commands Supported; Modbus Exception Responses - ABB SM500F User Manual

Field Mountable Videographic Recorder
SM500F
Appendix B – ModbusTCP Guide
B.1 Introduction
The instrument can be configured to act as either a ModbusTCP client or server.
If configured as a client the recorder collects data from ModbusTCP servers (or RTUs via a gateway) into its
Comms Analog and Comms Digital Channels.
If configured as a server the recorder responds to Modbus queries transferred via the ModbusTCP protocol
for the registers described in this appendix.
B.2 Modbus Commands Supported
The following Modbus commands are supported:
01 Read Coil Status – reads the on/off status of 16 consecutive digital states, starting at a specified
address. The instrument returns zeros for points which do not contain defined data.
03 Read Holding Registers – reads 8 consecutive analog values, starting from a specified address. The
instrument returns zeros for registers which do not contain defined data.
05 Force Single Coil – Sets the value of a single coil (digital signal) at the specified address. The data
value must be FF00Hex to set the signal ON and zero to turn it OFF. The instrument returns an
exception response if the register is not currently writable.
06 Preset Single Register – Sets the value of a single register (analog value) at the specified address.
The instrument returns an exception response if the register is not currently writable. Limits defined in
configuration are applied to the value before storage.
15 Force Multiple Coils – The instrument carries out updates that are valid and returns an exception
response if any of the coils are not currently writable.
16 Preset Multiple Registers – The instrument carries out updates that are valid and generates an
exception response if any of the registers are not currently writable.
Note. Negative numbers are represented in '2's complement' format, for example, 1000 = 03E8 (Hex),
–1000 = FC18 (Hex)
B.3 Modbus Exception Responses – Table B.1
If the instrument detects one of the errors shown in Table B.1 while receiving a message from the host
system, it replies with a response message consisting of the instrument's Modbus address, the function
code, the error code and the error check fields.
Code Name
01 Illegal Function
02 Illegal Data Address
03 Illegal Data Value
07 Negative Acknowledgement
08 Memory Parity Error
Table B.1 Modbus Exception Responses
IM/SM500F Issue 10.1
The message function received is not an allowable action
The address reference in the data field is not an allowable address
The value referenced in the data field is not allowable in the addressed slave
Received message error
Parity check indicates an error in one or more of the characters received
Appendix B – ModbusTCP Guide
Definition
47