MM74HC943N ,300 Baud ModemMM74HC943300BaudModemPRELIMINARYJanuary1988MM74HC943300BaudModemGeneralDescription
MM74HCT00M ,Quad 2 Input NAND GateFeaturesThe MM74HCT00 is a NAND gates fabricated using
MM74HC943N
300 Baud Modem
TL/F/5349
MM74HC943
Baud
Modem
PRELIMINARY
January 1988
MM74HC943 300 Baud Modem
General Description
The MM74HC943isafull 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 MM74HC943 utilizes advanced silicon-gate CMOS
technology. Switched capacitor techniquesare usedtope-
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 phoneline. Theycan performtwotofourwire
conversionand drivethelineata maximumofb9 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.
Features5V supply Drives 600Xatb9 dBmAll filterson chip Transmit level adjustment compatible with universal
service order code TTLand CMOS compatible logicAll inputs protected against static damage 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 signaling systems Remote process control
Connection and Block Diagrams
Dual-In-Line Package
TL/F/5349–1
Order Number MM74HC943
TL/F/5349–2
TRI-STATEÉ isaregistered trademarkof National SemiconductorCorporation.
C1995National SemiconductorCorporation RRD-B30M105/PrintedinU.S.A.
