The Digital Logic Level:Basic Logic Circuits

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Basic Digital Logic Circuits
• We have seen how to implement truth tables
and other simple circuits using individual gates.
• Few circuits are built like this in the realworld
• Instead modules containg many gates are used
• We will briefly look consider:
– Integrated Circuits
– Combinational Circuits
– Arithmetic Circuits
– Clocks



Integrated Circuits
• Gates are manufactured and sold in units
called Integrated Circuits, often called ICs or
chips.
• These are usually either square or rectangular
packages of either plastic or ceramic, and have
pins to connect them to the outside world.
• Dual Inline Packages or DIPs have two rows
of parallel pins



Multiplexers
• A multiplexer is a circuit with 2n data inputs, one
data output and n control inputs that select one
of the outputs.
• The selected data input is selected “gated”
(routed) to the output.
• The n inputs encode an n-bit number that
specifies which input is selected as the output.



Comparators
• A comparator is a circuit which compares two
input words and produces 1 if they are equal
and 0 if they are not equal.
• Based on the Exclusive-OR gate, which returns
0 if its inputs are equal and 1 if they are
unequal.
• A NOR gate decides whether to return 1 for
equality or 0 for inequality.