Controlling Gates

Enabling/Disabling Circuits&

Controlled Inverters

The idea here is to block or unblock propagation signals

An enable/disable signal serves two basic purposes:

1) One is to block /unblock a data signal from further propagation.2) The other one is to logically turn on/off logical devices (systems/subsystems)

What input combination of the enable signals will activate this gate?

{es1, es0} = {0, 1}

Determine the enabling input combination for these gates

{es2, es1, es0} = {1, 0, 1}

{es3, es2, es1, es0} = {0, 1, 0, 1}

Timing Waveform of a 2-to-1 Line Multiplexer

Timing Waveform of a 2-to-1 Line Multiplexer

Multiple Input Channels to a Single Output Channel

Can an OR gate can be used to combine different channels?

No. The problem is that channels might subdue each other

We may block a signal so that it does not subdue the other one

We may block a signal so that it does not subdue the other one

The enabling/disabling signals should be mutually exclusive. Why?

Enable Regions do not overlap so we are fine

Enable Regions overlap and this is a potential problem

Setting en = e_ch0 = e_ch1’ will give us mutually exclusive signals