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A gated SR latch circuit diagram constructed from AND gates (on left) and NOR gates (on right) A gated SR latch can be made by adding a second level of NAND gates to an inverted SR latch. The extra NAND gates further invert the inputs so a SR latch becomes a gated SR latch (a SR latch would transform into a gated SR latch with inverted enable).
The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output (1) results if both the inputs to the gate are LOW (0); if one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the negation of the OR operator.
Figure 2. The Set–Reset NOR latch example. A simple example of metastability can be found in an SR NOR latch, when both Set and Reset inputs are true (R=1 and S=1) and then both transition to false (R=0 and S=0) at about the same time.
A single NOR gate. A NOR gate or a NOT OR gate is a logic gate which gives a positive output only when both inputs are negative.. Like NAND gates, NOR gates are so-called "universal gates" that can be combined to form any other kind of logic gate.
A CMOS transistor NAND element. V dd denotes positive voltage.. In CMOS logic, if both of the A and B inputs are high, then both the NMOS transistors (bottom half of the diagram) will conduct, neither of the PMOS transistors (top half) will conduct, and a conductive path will be established between the output and Vss (ground), bringing the output low.
"A synchronous SR latch (sometimes clocked SR flip-flop) can be made by adding a second level of NAND gates to the inverted SR latch (or a second level of NOR gates to the direct SR latch)." The description does not match the circuit shown below. There are no NAND gates anywhere. A gated SR latch circuit diagram constructed from NOR gates.
First introduce the SR latch. Next introduce the clocked SR latch (i.e., SR latch with AND gates in front and a "clock" input). Next introduce the edge-triggered SR flip flop. Next introduce the edge-triggered JK flip flop. Add combinational logic to describe D and T flip flops.
Flip-flop excitation tables [ edit ] In order to complete the excitation table of a flip-flop , one needs to draw the Q(t) and Q(t + 1) for all possible cases (e.g., 00, 01, 10, and 11), and then make the value of flip-flop such that on giving this value, one shall receive the input as Q(t + 1) as desired.