Communication control system utilizing a shared buffer managed by high and low level protocols

A communication control system comprising:

• a system processor which processes communication data according to a higher level communication protocol;
• a system memory which stores programs executed by said system processor and data processed by said system processor;
• a communication controller, coupled to a transmission line and to said system memory, which transmits and receives a frame including said communication data on said transmission line while controlling said transmission line and processing said frame according to a lower level communication protocol;
• and
• a shared-buffer which stores said communication data, said shared-buffer being shared by said system processor and said communication controller,
• wherein said system processor reads out and writes in said communication data from and to said shared buffer according to a first buffer descriptor for managing said shared-buffer, and
• wherein said communication controller transfers said communication data between said shared-buffer and said transmission line according to a second buffer descriptor for managing said shared-buffer.