Writing Boolean Equations

Boolean equations represent combinational logic. Boolean equations are best represented using continuous assignment statements. Here is an example of a Gray code to binary code convertor using boolean equations. 

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It is illustrated in Section 3.4.4 by tracing the paths for leaking engine compression and applied to fault tree construction for the FFTF reactor Fullwood and Erdmann, 1974). The method involves writing Boolean equations for all paths whereby hazardous material may be released. It is primarily useful for enumerating release paths, but not for what started the release It was used to enumerate the possible paths for stealing nuclear bomb material from a facility. 

Using the top-down substitution method—actually writing Boolean equations from the top event down— we can write... 

Logic level, however, is not a natural level for system designers. For example, when we want to indicate that 32-bit values of two variables, a and 6, sholild be added and stored in the third variable, c, we simply write the expression c = a + 6. We do not write 32 Boolean expressions with up to 64 variables each to indicate this simple operation. It is very difficult to imagine having complex multi-chip systems described in terms of 1 million or more Boolean equations. 

In order to write down the microscopic equations of motion more formally, we consider a size N x N 4-neighbor lattice with periodic boundary conditions. At each site (i, j) there are four cells, each of which is associated with one of the four neighbors of site (i,j). Each cell at time t can be in one of two states defined by a Boolean variable where d = 1,..., 4 labels, respectively, the east, north,... 

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