That entrance guard monitors system is building world automatic system part , it is one kind of comprehensiveness , deals with multidisciplinary technologies such as electron , machinery , computer, communicate by letter , living things study of emulation. Naval is middle in dyadic networked entrance guard , the real time scene controls generally essential points realization. Self controller data stores capacities and the data-handling capacity all comparatively low because of entrance guard , needing to pass string communication makes the controller and super ordination machine be linked together therefore under ordinary circumstances, the data transfer what be collected is arrived at arrives at super ordination machine , carries out a data handling again on super ordination machine.
Have introduced that industry goes to the two in common use middle serial communication interface now in article: RS-232 and RS-485 communication interface. The monolithic machine having introduced that naval middle passes in entrance guard composes place machine down and , the chip changes into RS-485 communication string again process MAX485 before 485 signals will have change pass through the RS-232/RS-485 converter, change into RS-232 communication string signal , realize the request communicating by letter with PC machine, to realize remote communication.
Keywords：access control system ;Serial Communication; RS-232/RS-485 converter
