quartz/content/notes/boolean-equations.md
2022-07-19 20:41:12 +12:00

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boolean-equations
cosc204

Often used to describe/define Combinatorial logic circuits

Precedence

Precedence

  • NOT is unary, so it has the highest precedence
  • AND is mulitply, so it comes next
  • OR is like plusl, to it comes last

Precedence table|200

Creating boolean equations

example equation equivalent truth table

Creating boolean equations:

  • for each row where output is 1
  • write the equation as a function of the inputs (using AND)
  • Write the final equation, putting OR between each clause

De Morgan's Theorum

  • !(A + B) = A! & !B
  • !(A + B + C + ... + X) = !A & !B & !C & ... & !X
  • truth table
  • any boolean function can be represented as the sum of logical products
  • All combinatorial circuits can be described using just one gate type (either nand or nor) [^2]

[^2] : The Apollo Guidance Computer used about 5600 NOR gates and no other gate types!