Modicon M580 Plc Page 3-12 Communication

3/12 Functions (continued) I/O Scanning service The I/O Scanning Service is used to manage the exchange of remote I/O states on the Ethernet network after simple configuration, without the need for any special programming. I/O scanning is performed transparently by means of read/write requests according to the Modbus client/server protocol on the TCP/IP profile. This principle of scanning via a standard protocol enables communication with any device supporting Modbus TCP messaging in server mode. This service can be used to define: b A %MW word zone reserved for reading inputs b A %MW word zone reserved for writing outputs b Refresh periods independent of the PLC scan During operation, the module: b Manages TCP/IP connections with each remote device b Scans devices and copies the I/O to the configured %MW word zone b Feeds back status words used to check that the service is working correctly from the PLC application b Applies pre-configured fallback values if a communication error is detected A range of hardware and software products is available enabling the I/O Scanning protocol to be implemented on any type of device that can be connected to the Ethernet network. Characteristics b Under Unity Pro software, each station can exchange a maximum of: v 120 write words v 125 read words b Maximum size in the PLC managing the service: v For BME p 58 pp 40 processors, 1 Kword %MW in inputs and 1 Kword %MW in outputs with the manager PLC limited to 64 stations v For BME p 58 pp 20 processors and Ethernet communication module BMENOC03 pp , 2 or 4 Kwords %MW in inputs and 2 or 4 Kwords %MW in outputs with the manager PLC limited to 128 stations I/O Scanning service diagnostics I/O Scanning service diagnostics can be performed in one of five ways: b Via the application program from a specific PLC data zone b From the setup software debug screen b From the PLC system diagnostic function displayed by means of a web browser on a PC station b Using standard SNMP network management software INPUT OUTPUT + INPUT OUTPUT + A B A B Word table Read Write Ethernet Modbus/TCP Device input words/ output words Modicon M580 automation platform PlantStruxure Ethernet architectures Ethernet Modbus/TCP communication services Functions (continued) Modicon Premium, M580, or Quantum platform with I/O Scanner function (Transparent Ready class p 30) Device with Modbus/TCP messaging in server mode I/O Scanning service diagnostics 2 1 3 4 5 6 7 8 9 10 2 1 3 4 5 6 7 8 9 10

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