D E V I C E N E T   O P E R A T I O N S   S U P P O R T

The DeviceNet scanner communicates with the Modicon TSX Quantum PLC processor via discrete and block transfers over the backplane. A DeviceNet product may behave as a client, server, or both. The scanner communicates with the scanned devices via strobe, polled, change-of-state, and cyclic mes-sages. It uses these messages to solicit data from or to deliver data to each device on the network. Data received from the devices, or input data, is organized by the scanner and made available to the PLC processor. Data received from the PLC processor, or output data, is organized in the scanner and sent on to the network devices.

Strobed: Multi-cast message starts the scan cycle. Strobable slaves respond, based on their latency.

Polled: The Master interrogates each sensor/actuator according to the "polling list." Polls are sent out even as strobe responses are being received, as bandwidth allows.

Cyclic: Devices report data on a user-configured, time-increment basis (input or output). Cyclic data production is considered more efficient for applications with slowly changing analog I/O.

COS: A device reports its data only when there is a change. This is considered more efficient since only data changes are transmitted. It can be used along with Poll or Strobe.

Application-triggered data movement - Rather than being triggered by a Master, the movement of data is initiated by the application.