The bus technologies,especially the external bus technologies take a very important part in the instrument ATS,and are also considered as the bridge and tache of the ATS.

In the light of different equipments connected, BUS can be classified into internal BUS, on-board partial BUS, system BUS, and external BUS, among which the on-board partial BUS has the most significant influence to the performance of the system.

In the chip microcomputer system that may not make use of external bus(such as the system composed of AT89C51),data bus of ADC0809 can be directly connected with I/O port of the chip microcomputer,which controls ADC0809 directly.

It s the fundamental and foremost design for constituting an ADSP2106X application system to expand external memories and interfaces by the external bus port of ADSP2106X.

On the basis of briefing the function characteristics and corresponding signal actions of external bus port of ADSP2106X,taking the 8155H chip that is a programmable parallel interface adopting address and data multiplex mode bus as an example,an interface circuit between the 8155H and ADSP2106X is designed,and the composing principle and work process of this circuit are explicated.