73K224BL
V.22bis/V.22/V.21/Bell 212A/103
Single-Chip Modem w/ Integrated Hybrid
April 2000
DESCRIPTION
The 73K224BL is a highly integrated single-chip
modem IC which provides the functions needed to
construct a V.22bis compatible modem, capable of
2400 bit/s full-duplex operation over dial-up lines.
The 73K224BL is an enhancement of the 73K224L
single-chip modem which adds the hybrid hook
switch control, and driver to the 73K224L. The
73K224BL integrates analog, digital, and switched-
capacitor array functions on a single chip, offering
excellent performance and a high level of functional
integration in a 32-Lead PLCC and 44-Lead TQFP
package.
The 73K224BL operates from a single +5 V supply
for low power consumption.
The 73K224BL is designed to appear to the systems
designer as a microprocessor peripheral, and will
easily interface with popular single-chip micro-
processors (80C51 typical) for control of modem
functions through its 8-bit multiplexed address/data
bus or via an optional serial control bus. An ALE
control simplifies address demultiplexing. Data
communications normally occur through a separate
serial port.
(continued)
FEATURES
•
•
•
•
•
•
•
•
•
Includes features of 73K224L single-chip
modem
On chip 2-wire/4-wire hybrid driver and off
hook relay buffer driver
One-chip multi-mode V.22bis/V.22/V.21 and
Bell 212A/103 compatible modem data pump
FSK (300 bit/s), DPSK (600, 1200 bit/s), or
QAM (2400 bit/s) encoding
Software compatible with other TDK
Semiconductor K-Series one-chip modems
Interfaces directly with standard
processors (80C51 typical)
Parallel or serial bus for control
Selectable internal buffer/debuffer
scrambler/descrambler functions
and
micro-
All
asynchronous
and
synchronous
operating modes (internal, external, slave)
(continued)
BLOCK DIAGRAM
DTMF,
ANSWER,
GUARD &
CALLING
TONE
GENERATOR
FSK
MODULATOR
OH
BUFFER
SCRAMBLER
DI-BIT/
QUAD-BIT
ENCODER
FIR
PULSE
SHAPER
QAM/
DPSK
MODULATOR
EQUALIZER
FILTER
FILTER
8-BIT
µP
BUS
INTERFACE
FILTER
A/D
EQUALIZER
FILTER
ATTENUATOR
TXA1
2W/4W
HYBRID
DEBUFFER
DESCRAMBLER
DI-BIT/
QUAD-BIT
DECODER
DIGITAL
SIGNAL
PROCESSOR
RECEIVE
FUNCTIONS
TXA2
RXA
FILTER
FIXED
DEMODULATOR
AGC
GAIN
BOOST
TXD
RXD
SERIAL
INTERFACE
TONE
DETECTION
73K224BL
V.22bis/V.22/V.21/Bell 212A/103
Single-Chip Modem w/ Integrated Hybrid
DESCRIPTION
(continued
)
The 73K224BL is pin and software compatible with
the 73K222BL, allowing system upgrades with a
single component change.
The 73K224BL is designed to be a complete
V.22bis compatible modem on a chip. The
complete modem requires only the addition of the
phone line interface, a control microprocessor, and
RS-232 level converter for a typical system. Many
functions were included to simplify implementation
of typical modem designs. In addition to the basic
2400 bit/s QAM, 600/1200 bit/s DPSK and 300
bit/s FSK modulator/demodulator sections, the
device also includes synch/asynch converters,
scrambler/descrambler, call progress tone detect,
DTMF tone generator capabilities and handshake
pattern detectors. Test features such as analog
loop, digital loop, and remote digital loopback are
supported. Internal pattern generators are also
included for self-testing.
FEATURES
(continued)
•
•
Adaptive equalization for optimum perform-
ance over all lines
Programmable transmit attenuation (16 dB,
1 dB steps), selectable receive boost (+18
dB)
Call progress, carrier, answer tone,
unscrambled mark, S1, and signal quality
monitors
DTMF, answer and guard tone generators
Test modes available: ALB, DL, RDL, mark,
space, alternating bit, S1 pattern generation
and detection
CMOS
technology
for
low
power
consumption (typically 100 mW @ 5 V) with
power-down mode (15 mW @ 5 V)
TTL and CMOS compatible inputs and
outputs
•
•
•
•
•
FUNCTIONAL DESCRIPTION
HYBRID AND RELAY DRIVER
To make designs more cost effective and space
efficient, the 73K224BL includes the 2-wire to 4-
wire hybrid with sufficient drive to interface directly
to the telecom coupling transformers. In addition,
an off hook relay driver with 30mA drive capability
is also included to allow use of commonly
available mechanical telecom relays.
QAM MODULATOR/DEMODULATOR
The 73K224BL encodes incoming data into quad-
bits represented by 16 possible signal points with
specific phase and amplitude levels. The base-
band signal is then filtered to reduce intersymbol
interference on the band limited 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 73K224BL 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 base-band 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). Adaptive equalization is also used in
DPSK modes for optimum operation with varying
line conditions.
FSK MODULATOR/DEMODULATOR
The FSK modulator produces a frequency
modulated analog output signal using two discrete
frequencies to represent the binary data. The Bell
103 standard frequencies of 1270 and 1070 Hz
2
73K224BL
V.22bis/V.22/V.21/Bell 212A/103
Single-Chip Modem w/ Integrated Hybrid
FUNCTIONAL DESCRIPTION
(continued)
(originate mark and space) and 2225 and 2025 Hz
(answer mark and space) are used when this
mode is selected. V.21 mode uses 980 and 1180
Hz (originate, mark and space) or 1650 and 1850
Hz (answer, mark and space). 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 provide compromise delay
equalization and rejection of out-of-band signals.
Amplitude and phase equalization are necessary
to compensate for distortion of the transmission
line and to reduce intersymbol interference in the
band limited receive signal. The transmit signal
filtering corresponds to a 75% square root of
raised Cosine frequency response characteristic.
ASYNCHRONOUS MODE
The asynchronous mode is used for communication
with
asynchronous
terminals
which
may
communicate at 600,1200, or 2400 bit/s +1%, -
2.5% even though the modem’s output is limited to
the nominal bit rate ±.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 ±.01%. This signal is then
routed to a data scrambler and into the analog
modulator where quad-bit/di-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 passed through
without incorrectly inserting a stop bit.
The synch/asynch converter also has an extended
overspeed mode which allows selection of an output
overspeed range of either +1% or +2.3%. In the
extended overspeed mode, stop bits are output at 7/8
rising edge of TXCLK the normal width.
Both the synch/asynch 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 provided 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 at the same rate as it is input.
PARALLEL BUS CONTROL INTERFACE MODE
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 memory. The detect and
ID registers are read only and cannot be modified
except by modem response to monitored
parameters.
3
73K224BL
V.22bis/V.22/V.21/Bell 212A/103
Single-Chip Modem w/ Integrated Hybrid
SERIAL CONTROL INTERFACE MODE
The serial Command mode allows access to the
73K224BL control and status registers via a serial
control port. In this mode the AD0, AD1, and AD2
lines provide register addresses for data passed
through the AD7 (DATA) pin under control of the
RD and WR lines. A read operation is initiated
when the RD line is taken low. The next eight
cycles of EXCLK will then transfer out eight bits of
the selected address location LSB first. A write
takes place by shifting in eight bits of data LSB
first for eight consecutive cycles of EXCLK. WR is
then pulsed low and data transfer into the selected
register occurs on the rising edge of WR.
DTMF 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.
4
73K224BL
V.22bis/V.22/V.21/Bell 212A/103
Single-Chip Modem w/ Integrated Hybrid
PIN DESCRIPTION
POWER
NAME
GND
VDD
VREF
ISET
PIN
1
16
31
28
TYPE
I
I
O
I
DESCRIPTION
System ground
Power supply input, 5 V ±10% (73K224BL). Bypass with 0.1
and 22 µF capacitors to GND.
An internally generated reference voltage. Bypass with
0.1 µF capacitor to ground.
Chip current reference. Sets bias current for op-amps. The
chip current is set by connecting this pin to VDD through a
2 MΩ resistor. ISET should be bypassed to GND with a
0.1 µF capacitor.
PARALLEL MICROPROCESSOR CONTROL INTERFACE MODE
ALE
AD0-AD7
13
5-12
I
I/O
ADDRESS LATCH ENABLE: The falling edge of ALE latches
the address on AD0-AD2 and the chip select on
CS
.
ADDRESS/DATA BUS: These bi-directional tri-state
multiplexed lines carry information to and from the internal
registers.
CHIP SELECT: A low on this pin during the falling edge of
ALE allows a read cycle or a write cycle to occur. AD0-AD7
will not be driven and no registers will be written if
CS
(latched) is not active. The state of
CS
is latched on the
falling edge of ALE.
OUTPUT CLOCK: This pin is selectable under processor
control to be either the crystal frequency (for use as a
processor clock) or 16 times the data rate for use as a baud
rate clock in DPSK modes only. The pin defaults to the
crystal frequency on reset.
INTERRUPT: This open drain 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 low until the processor
reads the detect register or does a full reset.
READ: A low requests a read of the 73K224BL internal
registers. Data can not be output unless both
RD
and the
latched
CS
are active or low.
RESET: An active high signal on this pin will put the chip into
an inactive state. All Control Register bits (CR0, CR1, 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.
CS
23
I
CLK
2
O
INT
20
O
RD
15
I
RESET
30
I
5
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