| 摘要 |
PROBLEM TO BE SOLVED: To use a shift register at a normal time and also at an inspecting time. SOLUTION: A D/A converter 240 is composed of units U1 to Un and respective units U1 to Un are connected to respective data lines 6a. In the unit U1, an output signal W becomes an H level when a sampling SR1 and a read-out signal RE are both the H level. A selection circuit 242 controls connection states of the data line 6a and power source lines L1 to Ln based on the output signal W and various control signals. Especially, when the output signal W is the H level, it connects the data line 6a and the power source line L1. Consequently, when the read-out signal RE is made to be the H level at an inspecting time, voltages are successively read out from the respective data lines 6a.
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