PURPOSE: To check the frequency of a CR oscillator, which is self-oscillating in an IC, readily, by inputting a sampling frequency into a clock input terminal in a testing state.

CONSTITUTION: Terminals P1 and P2 are used to output the judge result of the frequency of a built-in CR oscillator 9. When the oscillator 9 is oscillating at a desired frequency, a sampling signal, whose frequency is higher than the oscillation frequency of the oscillator 9, is applied to a PG terminal from an external LSI tester. When the oscillation frequency of the oscillator 9 is lower than the desired frequency at this time, the width of a pulse during the high level period of the oscillation frequency becomes long. The number of the pulses at the high level of the sampling frequency is increased. Latch outputs at a high potential are taken out of the terminals P1 and P2. Meanwhile, when the oscillation frequency of the oscillator 9 is higher than the desired frequency, the pulse width during the high level period of the oscillation frequency becomes short. Then, the number of the pulses of the sampling frequency at the high level is decreased. The latch outputs at a low potential are taken out of the terminals P1 and P2.