1
Download SCADAPack E Series
Transcript
4 Modbus TCP Client I/O Board Interface The mtcp.. ISaGRAF boards are to be used by the SCADAPack E Series RTU to communicate via Ethernet or PPP serial interfaces with the Open Modbus/TCP protocol peripheral devices (herein described as PLCs). Note: Each the ISaGRAF application’s PLC I/O boards use a separate Modbus/TCP request to read or write its data. Improved Modbus communication efficiency can be achieved by grouping Modbus registers together and using less I/O boards with a larger number of channels (e.g. mtcp64ai), rather than more I/O boards with a smaller number of channels. A maximum of 100 Modbus/TCP Slave I/O Boards may be configured in total across both RTU ISaGRAF applications. ISaGRAF “Complex Equipment” types are comprised of configurations similar to I/O boards. Where a Complex Equipment type includes slave PLC I/O board configurations, each such I/O board configuration within the Complex Equipment type counts towards the limit of 100 Slave I/O boards. A corresponding pair of system points relates to each PLC Slave I/O board as described in section 8.7 - Open Modbus/TCP Server. Modbus/TCP boards utilize default IEC data types. Where applicable, the data type may be available for the user to choose. 4.1 Modbus/TCP Input Boards Modbus/TCP PLC Input Board variables are updated at the start of an ISaGRAF application scan. The value presented to the ISaGRAF variables is the value returned by the PLC from the previous read request. This read may have occurred during previous ISaGRAF application scans. The “data update rate” parameter on the I/O board sets the "scan" rate of the PLC data. The PLC communication status is updated if there is an error returned from the PLC, or no response from the PLC after a data request by the PDS. (See Section 11.1 - Modbus Status Values). The status is cleared by the SCADAPack E Series RTU upon successful communications. To catch transient errors you can use ISaGRAF code to store non-zero values. Figure 4-1: ISaGRAF Modbus/TCP board Input Board Parameters SCADAPack E Series Modbus PLC ISaGRAF Interface Reference January 19, 2006 16
