AS-I Couplers provide a means to route data between two PLC’s using AS-i. The couplers (similar to a DeviceNet spanner) directly connect AS-I networks, eliminating the need for a high level control network pyramid. This simple approach is extremely powerful and economical. It is simple because the coupler appears as a standard AS-I slave to each PLC; any AS-I scanner can send I/O data to the coupler without additional software or complex configuration procedures. It is economical because it replaces the high level control network, eliminating two control cards, wiring, conduit and programming.
Theory of Operation
A coupler transfers data between PLC A and PLC B by appearing as I/O to each PLC. The coupler immediately copies the output data from PLC A to the input data for PLC B. Similarly, PLC B’s output data is copied to PLC A’s input data. The data transfer may be four bits in each direction (the maximum allowable data size for one slave on one AS-I scan cycle).
The coupler optically isolates network A from network B; the networks do not interact electrically in any way. The coupler is powered internally by the AS-I power supply for the two connected networks.
Because the coupler is essentially two AS-I devices, one on network A and one on network B, it must be addressed as a slave on each network. The addresses for the two networks are independent of each other and do not need to be set to the same value.
The coupler is typically used to correct and coordinate multiple work cells.
Note: Physical AS-I connections are made via standard dual isolated port AS-I base modules (ASI-BM BW1181 for flat cable or ASI-BM BW1183 for round cable with screw terminal connections) on pages E105-106.