The Research And Design Of Usb Turn Multi-serial Port Controller Based On Cpld

Along with the development of modern information technology, USB has become the mainstream interface of the communication between the digital device. In many cases, we will face the problem that many serial port equipment should communicate with PC via USB. To meet the demand, this paper designs a communication protocol converters from USB to multiple serial,accomplishing the conversion from the USB to multiple serial.Designer makes a detailed analysis and verification about the system function. And the design follows the top-down concept. First, the whole system is divided into two modules according to the concrete function, one of which accomplishes the transparent data transmission from the USB to serial. This module depends on the USB bridging chip CH341 produced by Nanjing Qinheng Company to achieve USB conversion by using chip with a small amount of internal agreement via to periphery components. The other module realizes multiple serial port expansion by employing programmable device CPLD and VHDL.This paper accomplishes the design of the system by VHDL multi-serial port expansion. According to the specific requirements of the serial port expansion module, the partition is divided into three parts:serial data sending receiving module, data storage module and control module. All program compiles and simulation are completed in the simulation software MAX+plus II. Each part of the functions is simulated. Top level file connects the modules by using graphical editing method of and finally achieve the multi-serial port expansion of the function.Finally, the function of serial port expansion module is validated using CPLD experimental Circuit board and achieves the communication between computers and microcontroller of experimental board.