JPS5799841A - Automatic signal phase matching circuit - Google Patents

Abstract

PURPOSE:To automatically switch a working circuit and a stand-by circuit without instantaneous cut-off, by comparing phase of clock signals of both the circuits of the working circuit and the stand-by circuit, adjusting the phase automatically, and compensating an absolute time difference between signals of both the circuits. CONSTITUTION:A clock signal of the working circuit from a terminal 41, and a clock signal of the stand-by circuit, which has been inputted to a terminal 42 and has been phase-shifted by a phase-shifting circuit 403 are phase-compared by a phase comparator 401, its result is inputted to a phase-shifting controller 402, the circuit 403 is controlled by its output signal, and a clock signal of the stand-by circuit, which has been phase-matched with the clock signal of the working circuit is outputted to a terminal 43. A data signal of the stand-by circuit, whose variation range is N bits against a data of the working circuit is stored in an N bit shift register 501, and an optional one from outputs of this register 501 is selected 502 by a signal of a cyclic counter 505. A selected data and a data of the working circuit from a terminal 52 are bit-compared 503 by use of a phase matching clock, and in case they have coincided with each other continuously by the prescribed number of times, the counter 505 is stopped through a controlling circuit 504.