The flip-flop has many different implementations, its storage element is usually a Latch consisting of a NAND gate loop or a NOR gate loop with additional gates used to implement clocking.
32.
With two or more base resistors ( R 3 and R 4 ) instead of one, the inverter becomes a two-input RTL NOR gate ( see the figure on the right ).
33.
The only case where the output is high is when both transistors are off, which occurs only when both A and B are low, thus satisfying the truth table of a NOR gate:
34.
"' AND-OR-Invert "'( AOI ) logic and AOI gates are two-level compound ( or complex ) logic functions constructed from the combination of one or more AND gates followed by a NOR gate.
35.
A NOR gate is made into an OR gate by passing its output through a 1-input NOR gate; and it is made into an AND gate by passing each of its inputs through a 1-input NOR gate.
36.
A NOR gate is made into an OR gate by passing its output through a 1-input NOR gate; and it is made into an AND gate by passing each of its inputs through a 1-input NOR gate.
37.
A NOR gate is made into an OR gate by passing its output through a 1-input NOR gate; and it is made into an AND gate by passing each of its inputs through a 1-input NOR gate.
38.
This example assumes the Apollo parts inventory : 3-input NOR gates only, but the discussion is simplified by supposing that 4-input NOR gates are also available ( in Apollo, those were compounded out of pairs of 3-input NORs ).
39.
This example assumes the Apollo parts inventory : 3-input NOR gates only, but the discussion is simplified by supposing that 4-input NOR gates are also available ( in Apollo, those were compounded out of pairs of 3-input NORs ).
40.
Note that the use of 3-state logic for bus systems is not needed, and can be replaced by digital multiplexers, which can be built using only simple logic gates ( such as NAND gates, NOR gates, or AND and OR gates ).
