6.4 Logic gates Flashcards
What do truth tables do?
A truth table shows every possible combination of inputs and the corresponding output for a logic gate or logic circuit.
Describe the NOT gate. Describe its symbol?
The NOT gate has one input and one output. The gates output is always the opposite of the input. The symbol is a triangle point to the right with a circle at the point.
Describe the AND gate. Describe its symbol?
The AND gate has two inputs and outputs 1 if both inputs are also 1. It looks like a D shape with 2 inputs on the left and 1 output on the right.
Describe the OR gate. Describe its symbol?
The OR gate has two inputs. It will result in a 1 if either inputs are 1. It looks like a shield with 2 inputs on the left and 1 output on the right.
Describe the XOR gate. Describe its symbol?
It is known as exclusive or and has two inputs. It will only output 1 if either of the 2 inputs are 1 not both. It looks like a shield but with a line at the two inputs.
Describe the NAND gate. Describe its symbol?
NAND is short for NOT AND. It is an AND gate combine with a NOT gate. It has the opposite outputs as the AND gate. It looks like a D with a circle at the output.
Describe the NOR gate. Describe its symbol?
NOR is short for NOT OR. It is the combination of the OR gate with a NOT gate. It has the opposite outputs of an OR gate. It looks like a shield with a dot at the output.
What is an adder?
An adder is a logic circuit that can be used to add boolean values together. There are 2 types of adder. Full adder and half adder.
What is a half adder?
A half adder is a logic circuit with two inputs, two output and two logic gates. The circuit can be used to add two boolean values.
What is a full adder?
A full adder has three inputs and two inputs, enabling it to input two boolean values and a carry bit from a previous, less significant expression.
What is an Edge-triggered D-type flip-flop?
An edge-triggered D-type flip-flop is a logic circuit which can be used as a memory unit for storing the value of a single bit.
It has 2 inputs, one for data and another for clock signal. There is one output, which always hold the value of the stored bit.
How does a Edge-triggered D-type flip-flop work?
The clock signal is generated by the computer and alternates between 1 and 0 at a set frequency. The value of the stored bit is set to the value of the data input with each change of the clock signal. The clock signal can also be used to synchronise numerous flip-flops when they form part of a larger system such as a shift register.
