218L6S09 - ESE218 Spring 2009 Lecture 6 1 ESE218 Lecture 6...

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Unformatted text preview: 2/12/09 ESE218 Spring 2009 Lecture 6 1 ESE218 Lecture 6. Two-level implementations. Standard forms. Outline ¡ Implementations of algebraic expressions ¢ AND-OR vs NAND-NAND ¢ OR-AND vs NOR-NOR ¢ Open-drain, three-state and wired logic ¢ AOI and OAI ¡ Standard forms ¢ SOP and POS, form conversion ¡ Canonical standard forms ¢ minterms, sum of minterms ¢ Maxterms, products of maxterms ¢ form conversion ¡ Summary 2/12/09 ESE218 Spring 2009 Lecture 6 2 Implementations of algebraic expressions •Straightforward implementations •AND-OR for SOP form •OR-AND for POS form • Better implementations •NAND-NAND as equivalent to AND-OR •NOR-NOR as equivalent to OR-AND • THE BEST implementations •AND-OR-INVERT •OR-AND-INVERT •Circuits with open drain, wired logic Propagation delay Large Small 2/12/09 ESE218 Spring 2009 Lecture 6 3 NAND + inverter = AND AND gate is a two-stage circuit, it contains NAND gate and an inverter. The latter results in longer propagation delay compared to that in a single NAND gate a R +V DD b c=(ab)’ NAND R AND R +V DD a b ab (ab)’ NAND + Inverter 2/12/09 ESE218 Spring 2009 Lecture 6 4 AND-OR implementation SOP: F(A,B,C,D) = AB + CD A Too many inverters ⇒ longer propagation delay B C D 5 7408 1 2 3 7408 1 2 3 F AND =NAND+INVERTER OR = NOR+INVERTER Let us exclude the unnecessary inverters using properties of Boolean algebra! 2/12/09 ESE218 Spring 2009 Lecture 6 5 NAND-NAND implementation...
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This note was uploaded on 04/12/2009 for the course ESE 218 taught by Professor Donetsky during the Spring '08 term at SUNY Stony Brook.

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218L6S09 - ESE218 Spring 2009 Lecture 6 1 ESE218 Lecture 6...

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