Allen-Bradley 1771-SDN

The 1771-SDN module communicates with DeviceNet devices over the network to: respond as a slave, read inputs from a device, write outputs to a device, download configuration data, and monitor a device's operational status. The 1771-SDN module communicates with the processor in the form of Block Transfers (BT) and/or Discrete I/O (DIO). Information exchanged includes: device I/O data, status information and configuration data.

The 1771-SDN module communicates with a device via strobe, poll, change of state, and/or cyclic messages. It uses these messages to solicit data from or deliver data to each device. Data received from the devices, or input data, is organized by the 1771-SDN module and made available to the processor. Data received from your PLC-5 processor, or output data, is organized in the 1771-SDN module and sent on to your devices.

Your processor communicates with the 1771-SDN scanner module via block transfer reads, block transfer writes, and DIO transfers. Input data, gathered from the network's devices, is organized within the 1771-SDN and made available for the processor to "read". The 1771-OD module does not send data to your processor. Data transferred between the module and the processor must be initiated by the processor. Output data is sent, or "written", to the scanner by your processor. This data is organized in the 1771-OD module, which in turn passes the data on to your scanned devices via strobe, poll, change of state, or cyclic messages.