What SCADAPack E Modbus Client Method Should I use (Modbus Scanner or IEC Programming)?
SCADAPack E Modbus Client Operation
There are 2 methods to configure the SCADAPack E RTU to be used as a Modbus client. It can be done via IEC-61131-3 programs running on the controller, or it can be accomplished using the Modbus Scanner configuration in SCADAPack E Configurator. The method that you choose to implement depends on where the data you collect from the Modbus remote device is required
IEC 61131-3 Programs
Within IEC programs, there are an additional 2 methods. The legacy version uses the I/O devices to poll Modbus remote registers. A second method using Modbus set-up blocks was introduced in firmware 8.12.1. Both of these methods will return Modbus remote data into the IEC 61131-3 program variables. The data can be used in the programs for calculations and then applied to database points (using output I/O devices) if needed.
This method is useful if the Modbus remote data will be manipulated by an IEC 61131-3 program.
Modbus Scanner
A Modbus Scanner feature was also introduced in firmware 8.12.1. This lets a user configure Modbus polling within the SCADAPack E Configurator. Modbus remote data is returned directly into the SCADAPack E point database. If some of the data is needed in a IEC-61131-3 program, data can be mapped to program variables using input I/O devices.
This method is useful if the SCADAPack needs to act as a protocol converter between Modbus and DNP3 and/or the majority of the data will be sent to an upstream device as Modbus or DNP3.
Conclusion
Both methods can allow Modbus data to be used in IEC-61131-3 or converted to DNP3 points. The primary function of where the data will be used should be considered when choosing one of the 2 options.
Detailed operation of both methods is described in the SCADAPack E Documentation set (Included with the installation of SCADAPack E Utilities)