# TDC 311 Digital Logic. Truth Tables  AND  OR  NOT  NAND  NOR  XOR  XNOR.

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TDC 311 Digital Logic

Truth Tables  AND  OR  NOT  NAND  NOR  XOR  XNOR

Going from a truth table to a circuit ABCM00000010010001111000101111011111ABCM00000010010001111000101111011111

Is this circuit reduced?  Can apply Boolean algebra  Or use a Karnaugh Map

Common IC chips

Common chip terminology  SSI: 1-10 gates  MSI: 10-100 gates  LSI: 100-100K gates  VLSI: >100K  DIP  TTL  MOS  CMOS

Two Types of Digital Circuits  Combinational circuits – a series of logic gates  Sequential circuits – a set of logic gates with feedback  Let’s look at some common combinational circuits

Multiplexor  Control lines A,B,C control which input goes to output

Decoder

Comparator

One-bit ALU

Sequential Circuits  Used in computer memories  Basic unit called a latch  Circuits with feedback  Circuits move thru states

SR Latch S R ~Q Q S R Q ~Q 0 0 don’t 0 1 1 0 1 0 0 1 1 1 stable (or no change or quiescent) NAND gates can also be NOR gates

Clocked D Latch D Clock Q ~Q

Section of Computer Memory

Memory Chip 512K by 8 Memory chip 4096K by 1 Memory chip

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