Sr flip意思
"SR" in "SR flip-flop" stands for "Set-Reset". A flip-flop is a fundamental digital circuit that can store one bit of data. The SR flip-flop is one of the simplest types of flip-flops and is used as a basic building block in more complex sequential logic circuits.
The SR flip-flop has two inputs: Set (S) and Reset (R), and two outputs: Q and its complement Q' (sometimes denoted as ¬Q). The output Q follows the input S when the flip-flop is set (S is high and R is low), and it follows the input R when the flip-flop is reset (R is high and S is low). When both S and R are low, the flip-flop is in a stable state, and the output Q remains unchanged.
The behavior of an SR flip-flop can be described by the following truth table:
| S | R | Q(t+1) | Q'(t+1) |
|---|---|---|---|
| 0 | 0 | Q(t) | Q'(t) |
| 1 | 0 | 1 | 0 |
| 0 | 1 | 0 | 1 |
| 1 | 1 | Q(t) | Q'(t) |
As you can see from the truth table, when both S and R are high, the output Q follows the previous state Q(t). This is known as the "race condition" or "conflict condition", and it is a characteristic of the SR flip-flop.
The SR flip-flop is a level-triggered device, meaning that the inputs are sampled at the rising or falling edge of the clock signal. When the clock signal transitions, the flip-flop stores the values of S and R at that moment, and the outputs Q and Q' change accordingly.
SR flip-flops are relatively simple and can be easily constructed from simpler logic gates, such as NAND or NOR gates. However, they have a major drawback: they have a "race condition" or "synchronization" problem. If both S and R are asserted at the same time, the flip-flop can enter an undefined state, which is why they are not used in isolation in modern digital circuits. Instead, they are used as components in more complex circuits, such as master-slave flip-flops or JK flip-flops, which overcome this issue.