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+==============
+USB Device CDC
+==============
+
+USB Device CDC (Communication Device Class)is a part of the USB Device Stack library.
+It provides support for Abstract Control Model, which is one of the USB PSTN Device
+Models. The device uses both a Data Class interface and a Communication Class interface
+for it. For more detailed definition and description about this model, user can refer to
+the related chapter in <Universal Serial Bus Communications Class Subclass Specification
+for PSTN Devices, Revision 1.2>
+
+Features
+--------
+
+* Initialization/de-initialization.
+* Data transfer.
+* Callbacks management on:
+
+  * Transmission done
+  * Reception done
+  * Setting a new Line coding
+  * Line state changing
+
+Applications
+------------
+
+* Used as a vritual serial.
+
+
+Dependencies
+------------
+
+* USB Device Driver
+* USB Device Stack Core
+* USB Protocol CDC
+
+
+Limitations
+-----------
+
+* Only single instance can be supported, not applied for multiple case.
+* The INF and CAT file would be packed in atzip file. User can extract
+  them from "./usb/class/cdc/device".
+* If user wants to combine CDC with other classes into one device, USB
+  Device Stack Composite component should be added from the web page
+  rather than USB Device Stack CDC ACM.