14.1.27 Modbus measurement servers

The Modbus measurement server is an active and discoverable PVSR module which can monitor Modbus devices (for example PLCs) via a so called Modbus gateway. The measurement server takes into account the timeout value specified for the equipment. Beside the basic attributes, the equipment has the following additional parameters (the code of the parameter is given in parenthesis; see Subsection 7.5.6 on Parameters of non-SNMP data collectors):

·       Host (MODBUS EQ 1 HOST): this address of the Modbus gateway. Mandatory parameter

·       Port (MODBUS EQ 2 PORT): the port on which the Modbus gateway listens. Mandatory parameter, its default value is 502

·       Unit ID (MODBUS EQ 3 MODBUS_UNIT): the unit ID of the Modbus device we want to talk to through the Modbus gateway. Mandatory parameter

·       TCP/UDP (MODBUS EQ 4 TCP_UDP): whether the Modbus gateway uses the TCP or the UDP protocol. Mandatory parameter, its default value is TCP

·       Endianness (MODBUS EQ 5 ENDIANNESS): whether the communication should use the so called big or the little endian encoding. Mandatory parameter

• Equipment type and version (Z 01 EQ_TYPE): the type and the version of the Modbus device. Non-modifiable automatically discovered parameter

It is important to note that the Modbus protocol do not contain information about the meaning of the registers the system reads during monitoring, so it is recommended to create separate equipment templates for the different Modbus devices and to create the devices in PVSR using these templates (for example Schneider Electric PM710).