JPS573187A - Reference signal generating method - Google Patents

Abstract

PURPOSE:To generate a reference signal with a simple constitution through making special logical elements unnecessary, by delaying clocks from a clock oscillator of a laser printer by a delay element and by latching (n) pieces of clocks from respective taps of this element by the synchronizing signal of a synchronizing system. CONSTITUTION:A clock oscillator 17 which generates clocks of the same frequency as a reference signal is provided in a reference signal generating part of a signal control system of a laser printer, and the clock from this oscillator 17 is delayed in a delay element 18 by phase pi. This element 18 is provided with n/2 pieces of taps, and clocks C1-C5 phase-shifted by 2pi/n successively are generated from respective taps and are latched in latch circuits 19-23 due to FFs by the synchronizing signal from a synchronizing system. Clocks C1-C5 from the element 18 are controlled in AND circuits 34-38 by output signals of AND circuits 24-27 and 33, an AND circuits 44-48 are controlled by output signals of AND circuits 28, 30-32, and 39 inverted by NAND circuits 39-43, thereby outputting a clock approximating the synchronizing signal as the reference signal.