DeviceNet Modules, Series 90-30, Manual, GFK-2196

3Configuring a Cyclic I/O Messaging ConnectionIn Cyclic I/O Messaging as in Polled I/O Messaging, the DeviceNet master automatically sends amessage containing outputs to a device with a connection configured for Cyclic update. The devicesends back a response containing input data. Like Polling, Cyclic I/O Messaging requires 2messages to update the I/O data for a device. Unlike Polled messaging, Cyclic messaging can use adifferent interval as configured for each slave.DeviceNetMasterQueryResponseSlave 1QueryDeviceNet networkResponseSlave 2•••QueryResponseSlave nCyclic messaging can be appropriate for devices such as analog input sensors. For example, atemperature sensor might use Cyclic messages to report its measurements every 500ms. Cyclicmessaging can cut down on network traffic while accurately capturing certain types of inputmeasurements. This can also be more efficient for the application program in the PLC CPU. ACyclic I/O connection can also be used as a 'heartbeat' to provide assurance of a device's continuedoperation, with a Change-of-State I/O connection to the same device used to update its I/O state.To configure Cyclic I/O Messaging for a connection, select Cyclic on the Slave Properties menu.Cyclic I/O Messaging Screen for a Series 90-30 DeviceNet Master ModuleFor input resources, specify the number of data bytes the device will send to the master.For output resources, enter the number of bytes the device will consume from the master.If Acknowledge Suppress flag is selected, the DeviceNet master does not wait for an acknowledgemessage from the device.For Update, specify the interval in milliseconds at which the Series 90-30 DeviceNet master willupdate data for a network device. To select the fastest update rate possible, enter zero.3-20 Series 90®-30 Programmable Controller DeviceNet Modules – November 2002 GFK-2196