MM74HC942N ,MM74HC942 is a full duplex low speed modemMM74HC942300BaudModemJanuary1988MM74HC942300BaudModemGeneralDescription
MM74HC943N ,300 Baud ModemMM74HC943300BaudModemPRELIMINARYJanuary1988MM74HC943300BaudModemGeneralDescription
MM74HCT00M ,Quad 2 Input NAND GateFeaturesThe MM74HCT00 is a NAND gates fabricated using
MM74HC942N
MM74HC942 is a full duplex low speed modem
TL/F/5348
MM74HC942
Baud
Modem
January 1988
MM74HC942 300 Baud Modem
General Description
The MM74HC942isafull duplexlow speed modem.Itpro-
videsa300 baud bidirectional serial interfacefor data com-
munication over telephone lines and other narrow band-
width channels.ItisBell 103 compatible.
The MM74HC942 utilizes advanced silicon-gate CMOS
technology. Switched capacitor techniquesare usedtoper-
form analog signal processing.
MODULATOR SECTION
The modulator containsa frequency synthesizeranda sine
wave synthesizer.It producesa phase coherent frequency
shift keyed (FSK) output.
LINE DRIVER AND HYBRIDSECTION
Theline driverand hybridare designedto facilitate connec-
tiontoa 600X phone line. Theycan perform two-to-four-
wire conversionand drivethelineata maximumof0 dBm.
DEMODULATOR SECTION
The demodulator incorporates anti-aliasing filters,a receive
filter, limiter, discriminator, and carrier detect circuit. The
nine pole receive filter provides60dBof transmitted tone
rejection. The discriminatoris fully balancedfor stable
operation.
Features Drives 600Xat0 dBmAll filterson chip Transmit level adjustment compatible with universal
service order code TTLand CMOS compatible logicAll inputs protected against static damage g5V supplies Low power consumption Full duplex answeror originate operation Analog loopbackforselftest Power down mode
Applications Built-inlow speed modems Remote data collection Radio telemetry Credit verification Stand-alone modems Point-of-sale terminals Tone signalling systems Remote process control
TRI-STATEÉ isaregistered trademark ofNationalSemiconductorCorp.
Connection and Block Diagrams
Dual-In-Line Package
TL/F/5348–1
Top View
OrderNumberMM54HC942or
MM74HC942
TL/F/5348–2
C1995National SemiconductorCorporation RRD-B30M105/PrintedinU.S.A.
