Design and implementation of IRIG-B code time system using CPLD technique based on PCI bus

As general international standard, inter-range instrumentation group (IRIG) time codes were widely used in modern digital range, monitoring and measurement system, auto-control and commercial fields etc. A new design of IRIG-B code unified time system with high precision using complex programmable logic device (CPLD) technique based on PCI Bus is proposed in this paper. As compared with the original hardware electric circuit, the CPLD technique has lots of advantages such as smaller size, lower costs and the more reliable stability. Modulated and un-modulated IRIG-B time codes are respectively transmitting the information by varying the amplitude of a sine wave carrier and pulse duration modulation of a DC-signal (TTL). The sine carrier wave modulated signal is generated in a digital way by CPLD. The frequency of this signal is derived from the main oscillator of the system, which is disciplined by CNSS (compass navigation satellite system). This leads to a sine carrier wave with high accuracy. Data transfer is synchronized by the 1PPS (pulse per second) derived from the CNSS. Its various outputs like IRIG-B time code, serial time string and 1PPS (Accuracy of pulse outputs: plusmn <100 ns) can be used to synchronize other devices. IRIG-B code unified time system is designed for synchronizing the time of computers with PCI bus interface and for providing an application programming interface (API), which allows user to read the time of great accuracy and precision in his own application program.