| 摘要 |
PROBLEM TO BE SOLVED: To perform an AC test for an I/O buffer provided in a semiconductor integrated circuit device, at a low cost, efficiently, and with high accuracy. SOLUTION: In a test for the I/O buffer, a CPU 2 sets a selector control signal in a test control register 8 and causes selectors 11<SB>1</SB>to 11<SB>N</SB>to be connected so that I/O buffers 3a1 to 3aN have such connection to form a ring oscillator. Thereafter, the CPU 2 sets the control register 8 to enable an oscillation starting control signal, oscillates the ring oscillator, and performs count by means of a counter 15. When an arbitrary time period elapses, the CPU 2 reads a count value obtained by the counter 15 that counts, and it is previously determined by a test program whether the count value is within determination values. Acceptance is gained if the count value is within the determination values while it is determined to be rejected if the count value is beyond the determination values. COPYRIGHT: (C)2008,JPO&INPIT
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