73K324L

CCITT V.22bis, V.22, V.21, V.23, Bell 212A

Single-Chip Modem

April 2000

DESCRIPTION

The 73K324L is a highly integrated single-chip
modem IC which provides the functions needed to
design a Quad-mode CCITT and Bell 212A
compatible modem capable of operation over dial-up
lines. The 73K324L adds V.23 capability to the
CCITT modes of TDK Semiconductor Corporation's
73K224 one-chip modem, allowing a one-chip
implementation in designs intended for European
markets which require this added Modulation mode.
The 73K324L offers excellent performance and a
high level of functional integration in a single IC. The
device supports V.22bis, V.22, Bell 212A, V.21, and
V.23 operating modes, allowing both synchronous
and asynchronous operation as defined by the
appropriate standard.

The 73K324L is designed to appear to the Systems
Engineer as a microprocessor peripheral, and will
easily interface with popular one-chip
microcontrollers (80C51 typical) for control of
modem functions through its 8-bit multiplexed
address/data bus. A serial control bus is available
for applications not requiring a parallel interface. An
optional package with only the serial control bus is
also available. Data communications occurs through
a separate serial port.

(continued)

FEATURES

One chip Multi-mode CCITT V.22bis, V.22, V.21,

V.23 and Bell 212A compatible modem data pump

FSK (75, 300, 1200 bit/s), DPSK (600, 1200 bit/s),

or QAM (2400 bit/s) encoding

Pin and software compatible with other

TDK Semiconductor Corporation K-Series family
one-chip modems

Interfaces directly with standard

microprocessors (8048, 80C51 typical)

Serial and parallel microprocessor bus for

control

Selectable asynch/synch with internal

buffer/debuffer and scrambler/descrambler
functions

All synchronous (internal, external, slave) and

Asynchronous Operating modes

Adaptive equalization for optimum performance

over all lines

Programmable transmit attenuation (16 dB, 1 dB

steps), and selectable receive boost (+18 dB)

Call progress, carrier, answer tone, unscrambled

mark, S1, and signal quality monitors

DTMF, answer, calling, SCT and guard tone

generators

Test modes available: ALB, DL, RDL; Mark, Space

and Alternating bit pattern generators

CMOS technology for low power consumption

(100 MW @ 5 V) with power-down mode

(15 mW @ 5V)

4-wire full duplex operation in all modes

BLOCK DIAGRAM

SERIAL

I/F

FSK

MODULATOR

DIBIT/

QUADBIT

ENCODER

FILTER

DEBUFFER

DIBIT/

QUADBIT

DECODER

DE-

SCRAMBLER

FILTER

FIR

PULSE

SHAPER

QAM/

DPSK

MODULATOR

EQUALIZER

FILTER

TXA

DIGITAL

SIGNAL

PROCESSOR

RECEIVE

FUNCTIONS

A/D

EQUALIZER

FILTER

RXA

GAIN BOOST

TONE DETECTION

FIXED

DEMOD

FILTER

TXD

RXD

ATTEN

I/F

BUFFER

SCRAMBLER

DTMF,

ANSWER,

GUARD &
CALLING

TONE

GENERATOR

8 - BIT

BUS

AGC

6 dB

6 dB
GAIN

BOOST

73K324L
CCITT V.22bis, V.22, V.21, V.23, Bell 212A
Single-Chip Modem

DESCRIPTION

(continued)

The 73K324L offers full hardware and software
compatibility with other products in TDK
Semiconductor's K-Series family of single-chip
modems, allowing system upgrades with a single
component change. The 73K324L is ideal for use in
free-standing or integral system modem products
where full-duplex 2400 bit/s operation with Alternate
mode capability is required. Its high functionality, low
power consumption, and efficient packaging simplify
design requirements and increase system reliability.
A complete modem requires only the addition of the
phone line interface, a control microprocessor, and
RS-232 level converters for a typical system.
The 73K324L is designed to provide a complete
V.22bis, V.22, Bell 212A, V.21, and V.23 compatible
modem on a chip. Many functions were included to
simplify implementation in typical modem designs. In
addition to the basic 2400 bit/s QAM, 1200/600 bit/s
DPSK and 1200/300/75 bit/s FSK
modulator/demodulator sections, the device also
includes synch/asynch buffering, DTMF, answer,
soft carrier, guard, and calling tone generator
capabilities. Handshake pattern detectors simplify
control of connect sequences, and precise tone
detectors allow accurate detection of call progress,
answer, calling, and soft carrier turn off tones. All
Operating modes defined by the incorporated
standards are included, and Test modes are
provided. Most functions are selectable as options,
and logical defaults are provided. The device can be
directly interfaced to a microprocessor via its 8-bit
multiplexed address/data bus for control and status
monitoring. Data communications takes place
through a separate serial port. Data may also be
sent and received through the control registers. This
simplifies designs requiring speed buffering, error
control and compression.

FUNCTIONAL DESCRIPTION

QAM MODULATOR/DEMODULATOR

The 73K324L encodes incoming data into quad-bits
represented by 16 possible signal points with
specific phase and amplitude levels. The baseband
signal is then filtered to reduce intersymbol
interference on the bandlimited telephone network.
The modulator transmits this encoded data using
either a 1200 Hz (Originate mode) or 2400 Hz
(Answer mode) carrier. The demodulator, although
more complex, essentially reverses this procedure
while also recovering the data clock from the

incoming signal. Adaptive equalization corrects for
varying line conditions by automatically changing
filter parameters to compensate for line
characteristics.

DPSK MODULATOR/DEMODULATOR

The 73K324L modulates a serial bit stream into
di-bit pairs that are represented by four possible
phase shifts as prescribed by the Bell 212A/V.22
standards. The baseband signal is then filtered to
reduce intersymbol interference on the bandlimited
2-wire PSTN line. Transmission occurs on either a
1200 Hz (Originate mode) or 2400 Hz carrier
(Answer mode). Demodulation is the reverse of the
modulation process, with the incoming analog signal
eventually decoded into di-bits and converted back
to a serial bit stream. The demodulator also recovers
the clock, which was encoded into the analog signal
during modulation. Demodulation occurs using either
a 1200 Hz carrier (Answer mode or ALB Originate
mode) or a 2400 Hz carrier (Originate mode or ALB
Answer mode). The 73K324L use a phase locked
loop coherent demodulation technique that offers
excellent performance. Adaptive equalization is also
used in DPSK modes for optimum operation with
varying lines.

FSK MODULATOR/DEMODULATOR

The FSK modulator/demodulator produces a
frequency modulated analog output signal using two
discrete frequencies to represent the binary data.
V.21 frequencies of 980 and 1180 Hz (originate
mark and space), or 1650 and 1850 Hz (answer
mark and space) are used in V.21 mode. V.23 mode
uses 1300 and 2100 Hz for the main channel or 390
and 450 Hz for the back channel. Demodulation
involves detecting the received frequencies and
decoding them into the appropriate binary value.
The rate converter and scrambler/descrambler are
automatically bypassed in the FSK modes.

PASSBAND FILTERS AND EQUALIZERS

High and low band filters are included to shape the
amplitude and phase response of the transmit and
receive signals and to provide compromise delay
equalization as well as rejection of out-of-band
signals. The transmit signal filtering corresponds to a

% raised cosine frequency response

characteristic.

73K324L

CCITT V.22bis, V.22, V.21, V.23, Bell 212A

Single-Chip Modem

ASYNCHRONOUS MODE

The Asynchronous mode is used for communication
with asynchronous terminals which may transfer
data at 600, 1200, or 2400 bit/s +1%, -2.5% even
though the modem's output is limited to the nominal
bit rate ±0.01% in DPSK and QAM modes. When
transmitting in this mode the serial data on the TXD
input is passed through a rate converter which
inserts or deletes stop bits in the serial bit stream in
order to output a signal that is the nominal bit rate
±0.01%. This signal is then routed to a data
scrambler and into the analog modulator where di-bit
or quad-bit encoding results in the output signal.
Both the rate converter and scrambler can be
bypassed for handshaking and synchronous
operation as selected. Received data is processed
in a similar fashion except that the rate converter
now acts to reinsert any deleted stop bits and output
data to the terminal at no greater than the bit rate
plus 1%. An incoming break signal (low through two
characters) will be recognized and passed through
without incorrectly inserting a stop bit.
The SYNC/ASYNC converter has an extended
Overspeed mode which allows selection of an output
speed range of either +1% or +2.3%. In the
extended Overspeed mode, some stop bits are
output at 7/8 the normal width.
Both the SYNC/ASYNC rate converter and the data
descrambler are automatically bypassed in the FSK
modes.

SYNCHRONOUS MODE

Synchronous operation is possible only in the QAM
or DPSK modes. Operation is similar to that of the
Asynchronous mode except that data must be
synchronized to a clock and no variation in data
transfer rate is allowable. Serial input data appearing
at TXD must be valid on the rising edge of TXCLK.
TXCLK is an internally derived 1200 or 2400 Hz
signal in Internal mode and is connected internally to
the RXCLK pin in Slave mode. Receive data at the
RXD pin is clocked out on the falling edge of
RXCLK. The asynch/synch converter is bypassed
when Synchronous mode is selected and data is
transmitted out at essentially the same rate as it is
input.

PARALLEL CONTROL INTERFACE

Eight 8-bit registers are provided for control, option
select, and status monitoring. These registers are
addressed with the AD0, AD1, and AD2 multiplexed
address lines (latched by ALE) and appear to a
control microprocessor as seven consecutive
memory locations. Six control registers are
read/write. The detect and ID registers are read only
and cannot be modified except by modem response
to monitored parameters.

SERIAL CONTROL INTERFACE

The Serial Command mode allows access to the
73K324L control and status registers via a serial
control port. In this mode the A0, A1, and A2 lines
provide register addresses for data passed through
the DATA pin under control of the

and

lines.

A read operation is initiated when the

line is

taken low. The next eight cycles of EXCLK will then
transfer out eight bits of the selected addresss
location LSB first. A write takes place by shifting in
eight bits of data LSB first for eight consectuive

cycles of EXCLK.

is then pulsed low and data

transfer into the selected register occurs on the
rising edge of

TONE GENERATOR

The DTMF generator controls the sending of the
sixteen standard DTMF tone pairs. The tone pair
sent is determined by selecting TRANSMIT DTMF
(bit D4) and the 4 DTMF bits (D0-D3) of the TONE
register. Transmission of DTMF tones from TXA is
gated by the TRANSMIT ENABLE bit of CR0 (bit D1)
as with all other analog signals.

FULL DUPLEX OPERATION

Four-wire full duplex operation is allowed in all
modes. This feature allows transmission and
reception in the same band for four wire applications

only.

73K324L
CCITT V.22bis, V.22, V.21, V.23, Bell 212A
Single-Chip Modem

PIN DESCRIPTION

POWER

NAME

TYPE

DESCRIPTION

GND

System Ground.

VDD

Power supply input, 5V -5% +10%. Bypass with 0.22 µF and 22 µF capacitors to
GND.

VREF

An internally generated reference voltage. Bypass with 0.22 µF capacitor to GND.

ISET

Chip current reference. Sets bias current for op-amps. The chip current is set by
connecting this pin to VDD through a 2 M

resistor. Iset should be bypassed to

GND with a 0.22 µF capacitor.

PARALLEL MICROPROCESSOR INTERFACE

ALE

Address latch enable. The falling edge of ALE latches the address on AD0-AD2
and the chip select on

AD0- AD7

I/O /

Tristate

Address/data bus. These bidirectional tri-state multi-plexed lines carry information
to and from the internal registers.

Chip select. A low on this pin allows a read cycle or a write cycle to occur. AD0-
AD7 will not be driven and no registers will be written if

(latched) is not active.

is latched on the falling edge of ALE.

CLK

Output clock. This pin is selectable under processor control to be either the crystal
frequency (for use as a processor clock) or 16 x the data rate for use as a baud
rate clock in QAM/DPSK modes only. The pin defaults to the crystal frequency on
reset.

INT

Interrupt. This open drain weak pullup, output signal is used to inform the
processor that a detect flag has occurred. The processor must then read the detect
register to determine which detect triggered the interrupt.

INT

will stay active until

the processor reads the detect register or does a full reset.

Read. A low requests a read of the 73K324L internal registers. Data cannot be
output unless both

and the latched

are active or low.

RESET

Reset. An active high signal on this pin will put the chip into an inactive state. All
control register bits (CR0, CR1, CR2, CR3, Tone) will be reset. The output of the
CLK pin will be set to the crystal frequency. An internal pull down resistor permits
power on reset using a capacitor to VDD.

Write. A low on this informs the 73K324L that data is available on AD0-AD7 for
writing into an internal register. Data is latched on the rising edge of

. No data

is written unless both

and the latched

are low.

NOTE:

The Serial Control mode is provided by tying ALE high and

low. In this configuration AD7 becomes

DATA and AD0, AD1 and AD2 become the address only. See the serial time diagrams on page 23.

73K324L

CCITT V.22bis, V.22, V.21, V.23, Bell 212A

Single-Chip Modem

RS-232 INTERFACE

NAME

TYPE

DESCRIPTION

EXCLK

External Clock. This signal is used in synchronous transmission when the external
timing option has been selected. In the External Timing mode the rising edge of
EXCLK is used to strobe synchronous transmit data available on the TXD pin. Also
used for serial control interface.

RXCLK

O/Tristate Receive Clock Tri-statable. The falling edge of this clock output is coincident with

the transitions in the serial received DPSK/QAM data output. The rising edge of
RXCLK can be used to latch the valid output data. RXCLK will be valid as long as
a carrier is present. In V.23 or V.21 mode a clock which is 16 x 1200/75 or 16 x
300 Hz data rate is output, respectively.

RXD

Weak

Pull-up

Received Data Output. Serial receive data is available on this pin. The data is
always valid on the rising edge of RXCLK when in Synchronous mode. RXD will
output constant marks if no carrier is detected.

TXCLK

O/Tristate Transmit Clock Tri-statable. This signal is used in synchronous DPSK/QAM

transmission to latch serial input data on the TXD pin. Data must be provided so
that valid data is available on the rising edge of the TXCLK. The transmit clock is
derived from different sources depending upon the Synchronization mode
selection. In Internal Mode the clock is generated internally (2400 Hz for QAM,
1200 Hz for DPSK or 600 Hz for half-speed DPSK). In External Mode TXCLK is
phase locked to the EXCLK pin. In Slave Mode TXCLK is phase locked to the
RXCLK pin. TXCLK is always active. In V.23 or V.21 mode the output is a 16 x
1200/75 or 16 x 300 Hz clock, respectively.

TXD

Transmit Data Input. Serial data for transmission is input on this pin. In
Synchronous modes, the data must be valid on the rising edge of the TXCLK
clock. In Asynchronous modes (2400/1200/600 bit/s, or 75/300 baud) no clocking
is necessary. DPSK/QAM data must be +1%, -2.5% or +2.3%, -2.5 % in Extended
Overspeed mode.

ANALOG INTERFACE

RXA

Received modulated analog signal input from the phone line.

TXA

Transmit analog output to the phone line.

XTL1

XTL2

I/O

These pins are for the internal crystal oscillator requiring a 11.0592 MHz Parallel
mode crystal. Two capacitors from these pins to ground are also required for
proper crystal operation. Consult crystal manufacturer for proper values. XTL2 can
also be driven from an external clock.

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