| 摘要 |
PURPOSE:To improve the measurement of readout voltage margin of a semiconductor memory accurately and qualitatively, by performing the measurement through the continuous change of a readout power supply voltage and the collation of data measured with a reference data. CONSTITUTION:A processor 2 generates readout power supply voltage for initial setting from a D/A converter 6 via an input/output control circuit 4 and the voltage is applied to a memory 8 to be measured. The device 2 reads out a reference data from an internal memory 3, splits the data to each bit to count 1, 0 of each bit. The content of the memory 8 is read out and compared with the reference data. The number of discident bits is counted at every defective modes. That is, the comparison is made on a bit basis, and the data 1 changed into 0 is taken as relinquished bit and the data 0 changed into 1 is taken as quelled bit. When the check for all the readout addresses is finished, if the power supply voltage does not exceed the range of change, the voltage is slightly changed and the similar operation is repeated. This is made for the entire range of change. |
