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D flip-flop symbol. The D flip-flop is widely used, and known as a "data" flip-flop. The D flip-flop captures the value of the D-input at a definite portion of the clock cycle (such as the rising edge of the clock). That captured value becomes the Q output. At other times, the output Q does not change.
An asynchronous (ripple) counter is a "chain" of toggle (T) flip-flops wherein the least-significant flip-flop (bit 0) is clocked by an external signal (the counter input clock), and all other flip-flops are clocked by the output of the nearest, less significant flip-flop (e.g., bit 0 clocks the bit 1 flip-flop, bit 1 clocks the bit 2 flip-flop ...
Logic circuits are physical representation of simple logic operations, AND, OR and NOT (and their combinations, such as non-sequential flip-flops or circuit networks), that form a mathematical structure known as Boolean algebra. They are complete in sense that they can perform any deterministic algorithm.
In digital computing, the Muller C-element (C-gate, hysteresis flip-flop, coincident flip-flop, or two-hand safety circuit) is a small binary logic circuit widely used in design of asynchronous circuits and systems. It outputs 0 when all inputs are 0, it outputs 1 when all inputs are 1, and it retains its output state otherwise.
Simplified illustration of a logic cell. In general, a logic block consists of a few logic cells (each cell is called an adaptive logic module (ALM), a logic element (LE), slice, etc.). A typical cell consists of a 4-input LUT, a full adder (FA), and a D-type flip-flop (DFF), as shown to the right. The LUTs are in this figure split into two 3 ...
Synthesis software algorithmically transforms the (abstract) Verilog source into a netlist, a logically equivalent description consisting only of elementary logic primitives (AND, OR, NOT, flip-flops, etc.) that are available in a specific FPGA or VLSI technology.
An alternative solution to clock gating is to use Clock Enable (CE) logic on synchronous data path employing the input multiplexer, e.g., for D type flip-flops: using C / Verilog language notation: Dff= CE? D: Q; where: Dff is D-input of D-type flip-flop, D is module information input (without CE input), Q is D-type flip-flop output.
Unlike in software compiler design, where the register-transfer level is an intermediate representation and at the lowest level, the RTL level is the usual input that circuit designers operate on. In fact, in circuit synthesis, an intermediate language between the input register transfer level representation and the target netlist is sometimes ...