Delay Locked Loop, High-Level Data Link Control (HDLC)

DLL
Delay-Locked Loop (DLL) supports high-bandwidth data rates between devices. These DLLs are circuits that provide zero propagation delay, low-clock skew between output clock signals throughout a device, and advanced clock domain control. These dedicated DLLs can be used to implement several circuits that improve and simplify system level design.

High-Level Data Link Control (HDLC) 

• Developed by ISO
• Support Full Duplex Communication
• p2p and multipoint data links
• Use bits [bit oriented - not byte] to set flags

http://www.slideshare.net/AnandBiradar/hdlchigh-level-data-link-control