| 摘要 |
<p>PURPOSE:To instantaneously and stably operate the microcomputer even against abnormality of a voltage at the time when a power source is turned on by selecting one of several kinds of branch destination addresses to a reset input in accordance with a voltage level of a power supply voltage. CONSTITUTION:When a power source is turned on, and a power supply voltage is applied to a power supply voltage circuit 30, the power supply voltage circuit 30 detects whether it is above a set voltage value or not, and sends out a detecting signal to a reset vector selecting circuit 40. In the selecting circuit 40, in accordance with the contents of the detecting signal, a reset vector of one of a reset vector A store register or a reset vector B store register 20 is selected. In such a way, when the reset vector is selected at the time when the power source is turned on, and a reset signal 100 becomes active, the reset vector is sent out to a program counter 60 through a transmission gate 50. By receiving this reset vector from the counter 60, a start address of a program is outputted. As a result, an operation of the microcomputer is started.</p> |
