ADAPTER LD_UNLD

This adapter interface represents the operation of transferring a workpiece from an "upstream" piece of transfer equipment represented by a Model/View composite which acts as the provider of the plug adapter to a "downstream" piece of equipment represented by a second Model/View composite which acts as the acceptor with a corresponding socket adapter (see IEC 61499 for definitions of these terms).

As illustrated in the normal_operation sequence shown below, the typical operation of this interaction consists of the following sequence:

1. An event in the upstream equipment, e.g., arrival of a workpiece at the unload position, causes a LD event, typically interpreted as a "load" command, to the transmitted to the downstream equipment.
2. A subsequent event in the downstream equipment, e.g., completion of the load setup, causes an UNLD event, typically interpreted as a command to release the workpiece, to be sent to the upstream equipment.
3. Subsequently a CNF event, typically interpreted as confirmation of the workpiece release, is passed from the upstream to the downstream equipment to complete the operation.