1771-6.5.132, PLC-5 DeviceNet Scanner User Manual

Appendix DData Map ExampleThis appendix describes a basic mapping example that connects twoDeviceNet networks (channels A and B of the 1771-SDN scanner) to62 simple sensor-type devices. Each device sends one data byte thatcontains one data bit and one status bit.These are given in response to a strobe message. With channel Aonly, the scanner maps this data to the discrete I/O table if it isavailable; otherwise, the data is mapped to block transfer locations.MoreSee the 1771-SDN DeviceNet Scanner Installation Instructions (pub.no. 1771-5.14) for details on using block transfer read and writeoperations to communicate between your PLC-5 processor and1771-SDN scanner.Example InputMapping SchemeThis example’s input mapping scheme is a simplified and fixed mapof discrete input data and status bits for DeviceNet devices. It ismapped to discrete inputs and the device input data table. Anexample for each slot-addressing mode is given.Example Characteristics• strobe is used to query DeviceNet devices• poll is disabled• Devicenet A and B ports are connected to separate networks• the input data bit is fixed and occupies the lowest-order bit inthe lowest-order byte of the strobe (bit #0)• one bit of status data is accepted from each node responding tothe strobe• the status data bit is fixed and occupies the next lowest-order bitin the next lowest-order byte (after the input data bit) of thestrobe (i.e., bit #1)• input and status data bits accepted from each node are mappedto discrete inputs and the device input data table of the scanner• input and status data bits accepted from each node are fixed andpredefined1 Publication 1771-6.5.132 - June 2000