TRIGGER CIRCUIT OF WAVE FORM OBSERVATION APPARATUS

PURPOSE:To enable the accurate observation of signal transition state, by setting the point of time, when a first signal was generated, as a start point and performing sweeping or sampling from the point of time when the next signal was generated in the arbitrary indicated number of times. CONSTITUTION:A pulse generation circuit 7 detects the front edge part of the trigger pulse outputted from a trigger detection circuit 4 and generates a min. pulse at this point of time. Digital data 16 is inputted and set to a digital counter circuit 14 on the basis of this pulse. The data 16 comes to a set value N showing that a wave form is displayed or sampled from the point of time when what number of a pulse of a signal 2 counted from the generation of a signal 1 was generated. Thereafter, a trigger detection circuit 5 generates a trigger pulse every when the signal 2 exceeds a trigger level and the counter circuit 14 counters down at the front edge of said trigger pulse every when said trigger pulse is generated and, when the count content of said counter comes zero, a CR signal 18 is outputted. Generation circuits 8, 9 respectively output pulses and sweep signals on the basis of the signal 18. By this operation, the display or sampling of the part on and after what number of pulse of the signal 2 is enabled.