JPS5542443A - Clock supervisory system - Google Patents

Abstract

PURPOSE:To facilitate an easy cut-off of the fault and thus to realize an earlier detection of the clock-system fault by separating the input clock break detection circuit from the output clock phase step-out detection circuit of the phase lock oscillator, thus enhancing the reliability for supply and distribution of the clock. CONSTITUTION:Phase lock oscillator PLO3 is constituted with phase detector 31, LPF3(LPF32, oscillator 33 and local divider 34 each. Then the output clock frequency of oscillator 3 is divided through divider circuit 4 to deliver clock frequencies 4fN, 2fN and fN each to the output terminal. The step-out detection is given to oscillator 3 via output clock supervisory circuit 11 which supplies the output of detector 31, and the beat signal is generated in case the phase step-out is detected. At the same time, the phase step-out detection is given to the input clock via output clock supervisory circuit 11 which uses the output of lock route switch circuit 1 and circuit 4 as the input. Then the output of circuit 11 is applied to circuit 1 via clock route switch control circuit 2 to facilitate the switching of the clock route.