The high reliable timer is required in a synchronous measurement and in a distributed processing that uses the network computers. The precision of it is expressed with the stability of the frequency. The easiness of embedding, the low cost and down sizing are requested to the timer that is required in these various fields in addition to its precision. In this paper we propose a technique that realizes a high precision timer, which enables the synchronization in a many point with the low cost and with the small size. The proposed technique adopts a general PI control of VCO (Voltage Controlled Oscillator) based on GPS (Global Posi-tioning System). Also the controller of the timer that was developed is realized by software by using a DSP (Digital Signal Processor). The frequency stability that was obtained by the timer that was developed was 2.3×10-13
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