GE 90*-30 PLC Series User Manual

Also see for 90-30 PLC: Installation and Hardware Manual

Contents

2-6 Series 90™-30 PLC LONWORKS® Bus Interface Module User's Manual – June 1997 GFK-1322A2Sweep OperationThe data flow for information that is sent from the LON WORKS network to the PLC is handledseparately from the flow of data from the PLC to the LON WORKS network.Input data: When an input network variable is updated, the data associated with the networkvariable is copied into the proper location in a PLC input buffer. The Store Inputs routine is thencalled to update the data in the PLC at the next scan time.Output data: When the API callback notifies the LBIM that an output scan has arrived, the datais copied into a holding buffer. This buffer is then scheduled to be checked against the currentvalue of each output network variable. If the data is different, the network variable is updated overthe LON WORKS network if the Min Send Time for the network variable has expired (only if MinSend Time was configured). This prevents overloading the network with frequently changingdata.If a network variable is configured to be a SNVT_lev_disc or a SNVT_switch and is mapped intothe %I or %Q reference area, the data is converted to a bit. This conversion occurs when the datais moved to or from the PLC buffer.The total sweep time depends on the amount of reference memory used by the LBIM. This is amaximum of 1K words input and 1K words output, and is set when the LBIM’s Network Interfaceis configured.The I/O response times depend on the following factors:• number and size of network variables for which the LBIM is configured• rate at which network variables are updated• number of network variables that are bound• service type (ACKD, UNACKD) of each network variable• network bandwidth• network traffic• whether network variables are input or output network variables