| 摘要 |
<p>PURPOSE:To confirm stored code number of a code memory circuit by a tester by controlling a transfer gate and other transfer gate so as not to simultaneously become conductive in response to a potential level to be applied to test mode signal input terminals. CONSTITUTION:When a ROM code number stored in a code memory circuit 1 is confirmed, 5V is, for example, applied to a test mode signal input terminal PAD1. Then, transistors TRTrs 1, 2,..., 4 of a select circuit 2 of the circuit 1 are turned ON, whether the TR of the circuit 1 is of enhancement or depression can be decided from signal terminals PADs 2, 3,..., information of ROM code number is obtained, and the TR of a select circuit 3 becomes '0'. The PAD1 is fixed, for example, to 0V at the time of normal operation. Then, all the TRs of the circuit 3 become ON, the signals from the PADs 2, 3,... are input and output to be operated without fail, and the Tr of the circuit 3 becomes '0'. Thus, transfer gates can be controlled so as not to be conductive simultaneously in response to the applied potential level.</p> |
