本刊1993年第8期刊登的乔双同志“用CD4051提高8098单片机内10位A/D转换器分辨率的方法”一文,设计新颖,且电路简单.笔者按照文中介绍制作了电路,并按文中介绍软件流程图编了一段程序在SCB-Ⅱ型单片单板机上进行了仿真试验,效果不错,A/D转换结果也很准确.但是当把模拟输入电压Vi调到满量程值5V时,发现程序运行进入死循环.利用SCB-Ⅱ型机的单步运行功能检查发现原因是D_7(亦即IC_4的输出)始终为0,分析原文的硬件电路可知当Vi=5V时,不管n为哪一档,IC_3的输出V_(IN)始终大于或等于5V,所以IC_4的输出始终为0是必然的.再将Vi调到 Published in the eighth issue of 1993 Qiao Shuang comrades “CD4051 with 8040 to improve the resolution of 10-bit A / D converter method,” a novel design, and the circuit is simple.The author made the circuit according to the introduction of the article and press the The article describes the software flow chart compiled a program in SCB-Ⅱ type single-chip single board machine simulation test, the effect is good, A / D conversion results are accurate, but when the analog input voltage Vi transferred to the full scale value of 5V , Found that the program runs into an infinite loop.Using the SCB-Ⅱ-type single-step running function test found that the reason is D_7 (ie IC_4 output) is always 0, analysis of the original hardware circuit shows that when Vi = 5V, no matter n Which file, IC_3 output V_ (IN) is always greater than or equal to 5V, so the output of IC_4 is always 0. It is necessary to transfer Vi