基于MB90543的高性能GPS同步时钟研制

Development of high performance GPS synchronizing clock based on MB 90543

全球定位系统(GPS)同步时钟由GPS接收器、单片机及其外围电路组成。以MB90543为核心的时钟中心处理单元负责读取GPS接收器发送的数据信息并作适当处理,从中获取ASCII码国际标准时间的时间信息,经转换为BCD码后的串行时间信息供显示。该时钟选用可供嵌入式系统应用的M12 GPS接收器,可输出时间精度为1μs的秒脉冲。测频和数码管显示电路保证了电网频率的实时测量和显示。时钟软件包括初始化、接收器收/发、串口/CAN总线收/发、显示等子程序。采用串行通信方式授时,串行数据的收/发均采用中断方式,能提供日期和时间信息;而采用脉冲校时,可保证装置的校时误差小于50μs。在时钟装置中,采用以上2种综合校时方式。指出正确识别秒脉冲信号是确保同步校时的关键,软件及外部硬件计数阵列给秒脉冲信号加硬件窗的抗干扰措施效果良好。所设计的同步时钟投入运行后表明,符合设计要求。

The GPS（Global Position System） synchronizing clock is composed of GPS receiver, MCU and peripheral circuits. With MB90543 as the core,the central processing unit reads and processes data from GPS receiver to obtain ASCII-coded UCT（Universal Coordinated Time）,then converts it into BCD-coded serial time data for display. M12 GPS receiver outputs PPS（Pulse Per Second） with 1μs precision. Circuits of frequency measurement and LED（Light Emitting Diode） display ensure the real-time measuring and display of power frequency. The software includes subroutines of initialization,GPS receiver receiving/sending,serial port/CAN bus communication and display. When serial communication mode is adopted for time correction, interruptions are applied for receiving/sending serial data of date/time information. When pulse mode is adopted for time correction,the clock error is less than 50μs. Both modes are used in this clock. Correct PPS identification is the key to ensure clock precision. The anti-jamming measures are effective,i.e. software and hardware windows to PPS. The designed GPS synchronizing clock runs well.