Design Of 485 Communication Card Based On PCI Bus

PCI (Component Interconnect of Peripheral) bus is a popular bus facing the multimedia application. Nowadays it is the mainstream bus structure of the personal computer, and it has extensive prospects in embedded computer and industrial control computer applications. Due to its excellent performance, such as bandwidth, power dissipation, noise immunity and opening property, PCI wins rapidly increasing popularization and extensive applications.With the growth of the wide adoptions of PCI bus, its interface controller design is becoming more and more important. The strict characterizations and definitions of PCI make it is impossible to implement PCI by using traditional SSI or MSI device,lead to the more complex interface circuit that make the implementation of PCI in a impossible. According to the existing technologies, there are two methods to design PCI interface controller: One is to adopt special-purpose PCI chips;another is to use PLDs that support PCI bus electrical standards.Based on a deep study of PCI bus specification and ASIC design technology, a 485 communication card using PCI9052 chips is presented. To avoid the synchronous problem of data communication between computer and POS. this paper realizes the asynchronous problem by using RAM with double port. The new scheme can decrease the design of circuit and software.By using custom communication protocol, communication card and POS are composed of master-slave distributed network. One card can simultaneous communicate with two hundred and fifty-four POSes and one computer can simultaneous communicate with four cards. This card is using in OneCard system designed by the Little Sprite .Company. Reliability and practicability is proved by test.