Digital Components - Equality And Inequality Checks Flashcards
How does an equality check work? See page 94
For 2 bit checkers, 2 XNOR gates are required, one checks the MSBs and the other the LSBs.
If the MSBs or LSBs are the same, the output is HIGH.
If you want a single output, use an AND gate at the end.
Equality checkers are AKA Identity comparators
How does an inequality checker work? See circuit diagram on page 95
Inequality checkers also see if the two inputs are less than, equal to or greater than each other.
Both inputs go through an inverter, AND gates and a NOR gate to generate the output A<B, A=B or A>B
Why would a comparator IC have A=B tied to Vcc and A<b>B tied to GND?</b>
The comparator IC compares the bits starting from MSB and works its way down to LSB.
As soon as a difference is spotted, the comparator stops. In other words, once is finds that two bits of the same position are not the same, the comparator turns off because it has now found the difference and the outputs are connected to GND.
