| 摘要 |
<p>PURPOSE:To prevent the deterioration in A/D conversion precision by inhibiting the reading of a digital signal in the middle of A/D conversion and evading the generation of noise owing to through current in the middle of A/D conver sion. CONSTITUTION:An AD enable flag 9 which is set to a value corresponding to the enable/disable of an AD converter 3 connected in parallel to the input buffer 4 of the digital signal is provided for an analog/digital input terminal 2. A low active AD enable signal inverting the AD enable flag 9 is generated. The input buffer 4 is controlled by the AD enable signal. Output corresponding to digital input is not executed and the reading of the digital signal is inhibited even if a read signal (RD signal) is given from CPU 10 to the input buffer 4 at the time of A/D conversion.</p> |
