Chapter 2 Flashcards
logic circuits are made up of ____
logic gates - fundamental building blocks that carry out the logic operations
fundamental elements of a digital system are _____ and _____
input variable and output function
AND logic
if both (or all) inputs are 1, then output is 1
otherwise output is 0
represented by multiplication
two gates in series
OR logic
if any inputs are 1, then output is 1
if all inputs are 0, then output is 0
represented by addition
two gates in parallel
NOT logic
switches the input’s value from 0 to 1 or 1 to 0
aka the complement of a variable
NAND gate
output is complement of the AND of the inputs
NOR gate
output is the complement of the OR of the inputs
XOR gate
output is 1 if an odd number of input variables is 1
represented with a circle around an addition symbol
what is the xor function equivalent to
AB’ + A’B
truth table
used to demonstrate the output for each possible combination of inputs of a combinational circuit
universal logic gate
gates that can be used to implement the function of and, or, and not
NOT from NAND gates
both inputs of NAND gate are the same (split input into to wires, then feed into NAND)
AND from NAND gates
- first have A and B go into 1 NAND Gate, then feed output from 1st NAND gate (AB)’ into both inputs of 2nd NAND gate((AB’)’) = AB
OR from NAND gates
- first not both inputs
- then feed the not outputs into a third nand gate
NOT from NOR gates
- same as NAND
- connect inputs together
OR from NOR
- same as AND from NAND
- put inputs into one NOR gate then NOT the output from the first NOR gate
AND from NOR
- same as OR from NAND
- not each input, then feed them into the same NOR gate
NAND from NOR
- use same procedure to get AND from NOR, then NOT it
NOR from NAND
- use same procedure to get NOR from NAND then NOT it
logic network analysis - timing diagrams
tracks the sequential series of 0 and 1 for input and the output for those inputs
propogation delay
- t(pd)
- time for a change in the input of a gate to propagate to the output
- there are high to low and low to high propagation delays
what does the complement of a function look like?
- apply demorgans theorem until all ands have become ors and all ors have become ands
- the nots should change
why is simplifying logic circuits important?
- less cost
- less size
- less power consumption
- less delay
- speed is higher
minterms
- products of all variables
- labelled as a product of the variables, when variable is 0, it is x’, when the variable is 1, it is x