Programming instructions

74xx

 National Instruments Corporation 6-15 Multisim Component Reference Guide

6.4.30 74xx139 (Dual 2-to-4 Dec/DEMUX)

This decoder/demultiplexer contains two individual two-line to four-line decoders. It features

fully buffered inputs, each of which represents only one normalized load to its driving circuit.

2-to-4 decoder/demultiplexer truth table:

6.4.31 74xx14 (Hex INVERTER (Schmitt))

A key feature of this integrated circuit is its high noise immunity. Due the to the Schmitt-

trigger action, this device is ideal for circuits that are susceptible to unwanted small signals,

such as noise.

INVERTER gate truth table:

6.4.32 74xx145 (BCD-to-Decimal Dec)

The BCD-to-decimal decoder/driver consists of eight inverters and ten four-input NAND

gates. These decoders feature high-performance, n-p-n output transistors designed for use as

indicator/relay drivers or as open-collector logic-circuit drivers.

INPUTS OUTPUTS

ENABLE SELECT

B A Y0 Y1 Y2 Y3

1 XX1111

0 000111

0 011011

0 101101

0 111110

The voltage threshold levels are as follows:

VT- = 0.95V (at 5 Volt test condition)

VT+ = 1.8V (at 5 Volt test condition)

ComponentRef.book Page 15 Thursday, December 7, 2006 10:12 AM