The importance of the logical truth table and the delay of 74hc4051.

One about 74hc4051:

In the/e=0 enable output condition, the S2s1s0 three values, can be selected through Y0~y7 one of the channels from the z output.

Second: The problem is proposed: In accordance with the IC given the truth table for chip operation, the output logic is completely not

Three: Analysis: How to determine the selection of a channel, this channel is really conduction? My project is to use Y0~Y7 as the channel for AD

3.1 Pass level logic? no! because the Y0~y7 is the same as the ground voltage when it is not on, the z-to-ground level is a value, and when the conduction is just Z-to-ground and the y0~y7 to the ground becomes the same, or is not sure that the channel conduction.

3.2 By applying different mode values to ad after conduction, see that the channel has changed significantly to determine which S2S1S0 table value corresponds to the current ad channel, yes!

Four: According to the measured corresponding re-layout truth table, found does not correspond to, like ginseng and there are new changes, what is the reason?

V: The root cause: is the 74hc4051 channel switch to give appropriate delay, according to the size of the load capacitor to adjust. When the delay is added, it does not change back and forth like ginseng.

VI: Summary:

Because of the capacitive load of the existence of the load, do not give the appropriate delay on the direct operation, the conclusion is not the value of their own conceived channel, the natural change every time, especially in the identification of the channel when the number of elements is small, the interference of several channels is the same, which adds confusion to the channel identification

The importance of the logical truth table and the delay of 74hc4051.