| 摘要 |
<p>PURPOSE:To select pull-up resistances with software by providing a voltage converting circuit which converts the high level of the output voltage of a register from VDD to a voltage supplied from the external. CONSTITUTION:When the output of a register 3 is in the low level, the output of a voltage converting circuit 4 goes to the level of VSS, and a pull-up resistance 2 is made non-conductive because the gate potential of a pull-up resistance 1 goes to VSS. When the output of the register 3 is in the high level, the output of the voltage converting circuit 4 goes to the level of VP, and the pull-up resistance 1 is made conductive and the high level is equal to the level of VDD because a voltage higher than the sum of VDD and the threshold voltage of an N-channel MOS transistor is applied by VP. Thus, pull-up resistances are made selectively conductive or non-conductive by software.</p> |
