Full adder

The logical operators get directly mapped onto primitive logic gates in hardware. Here is a model of a full-adder using continuous assignment statements. 

A module instantiation statement can be written within a module declaration. A synthesis system treats such a module instance as a black box and does not take further action, that is, the module instance appears in the synthesized netlist as if it were a primitive component. Here is an example of a full-adder module that contains one module instantiation statement. Notice that in the synthesized netlist, shown in Figure 2-67, the module MyXor appears just as it is described in the top level module FullAdderMix. 

Another approach is to write a test bench a test bench is a model written in Verilog HDL that applies stimulus, compares the output responses, and reports any functional mismatches. Figure 5-3 shows such a scenario. A test bench for a full-adder is shown next. The stimulus is read from a vector file Inputs.vec its contents are of the form ... 

Fig. 11. A full adder for the addition of multi-digit numbers. The three inputs are II and 12 -the digits to be added - and Cl - the carry digit from the previous pair of inputs. Through a combination of two half adders and a further XOR gate, connected in both series and in parallel, the sum and carry outputs of the addition are produced...

Design of a self-assembling self-repairing one-bit full-adder... 

Every cell determines its state from two of its immediate neighbours. Other than pwwer and dock lines there are no global connections required for the CA to converge to its correct state. If a full-adder is to be implemented on such a platform, it would ideally not require any global connections either. 

The cell has no bi-directional communications it relies on two-inputs and two-output lines in a feed-forward arrangement in order to converge. Likewise an ideal full-adder design should be built on this arrangement. This means each component cell cannot feedback data to a cell that lies earlier on on the data path. 

Each cell has two output lines, but the state-output is common to both. Again, the most appropriate implementation of a full-adder design will piggy-back these existing communications lines and not require additional networking. One consequence of this is that no two data lines can cross. 

Because we want this full-adder to be scalable, the one-bit full-adder modules should be stackable, that is, if the modules are arranged one on top of one another, the carry-out lines should connect to the carry-in line beneath it. 

In order for the full-adder to be scalable, the CA state pattern must repeat until it uses all the available cells. 

The cell connected to input A of the full-adder must be to below a state 7. ... 

The top-left cell of the first bit of the full-adder must be below a state T. 

A full adder example, the Intel 18212, a bus interface example, a controlled counter example, a fifth-order digital elliptic wave filter example, a 16-point FIR filter example, a 256-point DFT-algorithm example, and a B-spline FIR filter example. 

Figure 1.5 The full adder circuit is built from two half adders.

An example algorithm is the one-bit full adder which is shown in Table 9.2 for the classical and quantum forms of the algorithm [21]. The one-bit adder adds three one-bit numbers (A, B and Qn) to produce output bits (S = A + B - -Cin and Cout)- The carry (Qn and Cout) are bits from previous or future additions, respectively, as would occur if the sum of the numbers, S, is greater than or equal to two. This is analogous to addition in the decimal system, as when the number is greater than or equal to 10 then we carry a 1 to the next place value. The quantum form of the one-bit adder must include one additional input (D) and two extra... 

Table 9.2 Description of the classical and quantum one-bit full adder algorithm...

Next consider a 1-bit adder, which is very similar to a half adder. The difference is that a 1-bit adder, or full adder, has three inputs, one of which is for a carry-in. Hence, with a full adder every 2-bit number is a possible output. 

A 1-bit full adder is formed using the SUM and carry out COUT equations SUM AxorBxorCfN (6.1)... 

The adder itself is contained in Figure 8.13. The ARITH UTILS package contains the two procedures RC ADDER and FULL ADDER. The first defines an N-bit ripple-carry adder and the second a single-bit full adder procedure. These procedures are similar to fiiose constructed as functions... 

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