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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.
The flip-flop is the next significant template; in Verilog, the D-flop is the simplest, and it can be modeled as: reg q ; always @( posedge clk ) q <= d ; The significant thing to notice in the example is the use of the non-blocking assignment.
AND gated J-K master-slave flip-flop, asynchronous preset and clear (improved 74L72) (16) BL54L67Y: 74L68 2 dual J-K flip-flop, asynchronous clear (improved 74L73) (18) BL54L68Y: 74LS68 2 dual 4-bit decade counters 16 SN74LS68: 74L69 2 dual J-K flip-flop, asynchronous preset, common clock and clear (18) BL54L69Y: 74LS69 2 dual 4-bit binary ...
In a sequential digital logic circuit, data is stored in memory devices called flip-flops or latches. The output of a flip-flop is constant until a pulse is applied to its "clock" input, upon which the input of the flip-flop is latched into its output. In a synchronous logic circuit, an electronic oscillator called the clock generates a string ...
The 7400 series contains hundreds of devices that provide everything from basic logic gates, flip-flops, and counters, to special purpose bus transceivers and arithmetic logic units (ALU). Specific functions are described in a list of 7400 series integrated circuits. Some TTL logic parts were made with an extended military-specification ...
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 ...
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.
Of course, the particulars of the available logic gates and flip-flops are specific to each manufacturer and product family. But the general idea is always the same. Most SPLDs use either fuses or non-volatile memory cells (EPROM, EEPROM, Flash, and others) to define the functionality. These devices are also known as: Programmable array logic (PAL)