Design and Implementation of Micro-controller's Serial Port Expansion Based on ST16C554D

On the basis of the internal structure and registers related with communication of ST16C554D.The application hardware circuit and an initialization software program of communication between AT89S52 and more serial interface using ST16C554D is introduced.And in practice by configuring an RS232 standard serial channels and an RS422 standard serial channels to verify the feasibility,stability and practicality of the system.