146_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES

146_pdfsam_VLSI TEST PRINCIPLES & ARCHITECTURES -...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Logic and Fault Simulation 115 3.2.3.1 Truth Tables Using the truth table is the most straightforward way to evaluate logic elements. Assuming only binary values, an n -input combinational logic element requires a 2 n -entry truth table to store the output value with respect to all possible input combinations. (For a sequential element, n corresponds to the number of its input and state variables.) In practice, the truth table is stored in an array of size 2 n .To access the array, the values of the n input variables are packed in a word that serves as the index to access the array. For example, consider the array T NAND3 to store the truth table of a three-input NAND gate. Then, the output value with respect to input pattern 010 is obtained by: T NAND3 ± 010 2 ² = T NAND3 ± 2 ² where the subscript 2 indicates the binary number system. For a multivalued logic system with k symbols, the required array size for an n -input element is calculated as follows. Let m be the number of bits needed to code the k
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Ask a homework question - tutors are online