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For example, an 8:1 multiplexer can be made with two 4:1 and one 2:1 multiplexers. The two 4:1 multiplexer outputs are fed into the 2:1 with the selector pins on the 4:1's put in parallel giving a total number of selector inputs to 3, which is equivalent to an 8:1.
Input 1 (I 1) is A; that has control input D that is also connected to the initial carry, then the modified adder performs addition when D = 0, or; subtraction when D = 1. This works because when D = 1 the A input to the adder is really A and the carry in is 1. Adding B to A and 1 yields the desired subtraction of B − A.
A full adder can be viewed as a 3:2 lossy compressor: it sums three one-bit inputs and returns the result as a single two-bit number; that is, it maps 8 input values to 4 output values. (the term "compressor" instead of "counter" was introduced in [13])Thus, for example, a binary input of 101 results in an output of 1 + 0 + 1 = 10 (decimal ...
The skip-logic consists of a -input AND-gate and one multiplexer. T S K = T A N D ( m ) + T M U X {\displaystyle T_{SK}=T_{AND}(m)+T_{MUX}} As the propagate signals are computed in parallel and are early available, the critical path for the skip logic in a carry-skip adder consists only of the delay imposed by the multiplexer (conditional skip).
In the conditional sum adder, the MUX level chooses between two n/2-bit inputs that are themselves built as conditional-sum adder. The bottom level of the tree consists of pairs of 2-bit adders (1 half adder and 3 full adders) plus 2 single-bit multiplexers. The conditional sum adder suffers from a very large fan-out of the intermediate carry ...
The very fastest shifters are implemented as full crossbars, in a manner similar to the 4-bit shifter depicted above, only larger. These incur the least delay, with the output always a single gate delay behind the input to be shifted (after allowing the small time needed for the shift count decoder to settle; this penalty, however, is only incurred when the shift count changes).
To achieve better performance in the same area or the same performance in a smaller area, multiplier designs may use higher order compressors such as 7:3 compressors; [8] [7] implement the compressors in faster logic (such transmission gate logic, pass transistor logic, domino logic); [13] connect the compressors in a different pattern; or some ...
Every arbitrary BDD (even if it is not reduced or ordered) can be directly implemented in hardware by replacing each node with a 2 to 1 multiplexer; each multiplexer can be directly implemented by a 4-LUT in a FPGA. It is not so simple to convert from an arbitrary network of logic gates to a BDD [citation needed] (unlike the and-inverter graph).