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Unformatted text preview: Design Example for LASI Layout A. Setting up the Pulldown and Pullup Logic Functions The design begins with the logic function to be performed. The logic functions Fpd and Fpu (for the pulldown and pullup sections) correspond to connecting the output to either ground (Fpd true) or V++ (Fpu true), respectively. For this example, an arbitrary logic function of five inputs is used. We will start with the logic function for the pulldown section (which will be constructed from NMOS transistors) and use F pd = A • B + C ( ) [ ]+ D • E [ ] . I have used brackets and parentheses to ensure that in the next step we make the proper transformation using D'Morgan's rule. When Fpu is TRUE, the output is pulled to ground (logic "0"). If developing the Boolean equation from a truth table, you would select the lines corresponding to an output equal to logic "0", in contrast to the usual approach for sum-of- products forms obtained by selecting lines corresponding to an output equal to logic "0". The products forms obtained by selecting lines corresponding to an output equal to logic "0"....
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This note was uploaded on 10/27/2009 for the course ECE 5 taught by Professor Chavez during the Spring '09 term at Stevens.
- Spring '09