A new approach to realize UART

In order to connect DSP which has synchronous serial ports to the devices implementing asynchronous communications protocol, a method to implement UART communications based on programmable logic device is proposed in the paper. In the proposed method, the core function of UART is integrated in CPLD with VHDL. Firstly, UART data frame format and operational principle of UART were introduced after reviewing some methods to realize UART. The methods to implement UART transmitter, UART receiver and baudrate generator using VHDL were illustrated in detail. Then pre-simulation and synthesize of VHDL program were executed. Finally, the test with bit error rate was carried out on physical system. Experimental results indicate that 75 percent of the GLB are used by UART, and the bit error rate is less than 10^-9. The experiment was implemented utilizing the RS-422 protocol and the baudrate is 62.5kb/s. The proposed method can satisfy the system requirements of high integration, stabilization, low bit error rate, strong anti-jamming and low cost.