When a class instance is created, a control structure is allocated and associated to a specific class instance. The class uses this control structure for its internal operations. All the Micrium USB classes define a class control structure data type. shows the declaration of such data structure.
During the communication phase, the class communication structure is used by the class for data transfers on the endpoints. It allows you to route the transfer to the proper endpoint within the interface. There will be one class communication structure per configuration to which the class instance has been added. presents this structure.
Micrium’s USB classes define a class state for each class instance created. The class state values are implemented in the form of an enumeration:
defines a class state machine which applies to all the Micrium classes. Three class states are used.