| 摘要 |
<p>PURPOSE:To improve the reliability of the operation of the microcomputer by setting a test mode only when a potential inputted to the potential setting terminal of an A/D converter is inverted. CONSTITUTION:When A/D converting operation is performed, potentials VVR and VAGND are so set that VVR>VAGND for the generation of a reference potential for the A/D conversion. When the A/D converting operation is not performed, there is possibly a case where VVR=VAGND. Namely, VVR>=VAGND in a normal use state without fail. In this state, the gate-source potential of an NMOS transistor TR does not exceeds the gate inverted potential of an N-MOS, so the TR turns off. In this OFF state, the drain side (point A) of the TR is pulled up through a high resistance R, so the potential level at the point A is an H level. This state is sent as an L level to a test circuit through an inverter INV. Consequently, the test circuit is not made active.</p> |
