V.34/Group 3 High Performance Fax Modem Family
DMA Support for Interrupt Request Lines
DMA support is available in synchronous data modes.
When DMA support is enabled, the modem /RI and
/DSR lines are assigned to Transmitter Request
(TXRQ) and Receiver Request (RXRQ) hardware
output interrupt request lines, respectively. The TXRQ
and RXRQ signals follow the assertion of the Transmit
Data Buffer Empty (TDBE) and Receive Data Buffer
Full (RDBF) interrupt bits, thereby allowing the
DTE/host to respond immediately to the interrupt
request without masking out status bits to determine
the interrupt source.
Quick Start for V.34 Half-Duplex
V.34 Fax Quick Startup eliminates the V.8 phase 1
segment and uses a shortened training sequence
during phase 3, which can save up to 50% of the initial
Phase1 to Phase 4 start up time for normal V.34 half-
ADPCM Voice Mode
The Adaptive Differential Pulse Code Modulation
(ADPCM) voice coder and decoder (codec)
compresses and decompresses voice signals for
efficient digital storage of voice messages. The codec
operates at 28.8 kbps, 21.6 kbps, or 14.4 kbps
(4-bit, 3-bit, or 2-bit quantization, respectively) with
an 8.0 kHz sampling rate.
Caller ID Demodulation
Caller ID information can be demodulated in the
V.23 1200 receive configuration and presented to the
DTE/host in serial (RXD) or parallel (RBUFFER) form.
Call Waiting Detector
A tone detector is provided to perform call waiting
detection and is available in V.90, V.34, V.32bis, V.32,
V.17, V.29, and V.27ter modes. By default, call waiting
tone levels down to approximately –28 dBm can be
detected. The detector can tolerate near-end echo
levels up to 10 dB above the call waiting tone level.
Telephone Line Interface
Line Transformer Interface. V.90/V.34 places high
requirements upon the Data Access Arrangement
(DAA) connection to the telephone line. Due to the
wider bandwidth requirement of V.90 and V.34, the
DAA must maintain linearity from 150 to 3950 Hz for
V.34, and from 10 to 4000 Hz for V.90.
Relay Control. Direct control of the off-hook and
talk/data relays is provided. Internal relay drivers allow
direct connection to the off-hook and talk/data relays.
The talk/data relay output can optionally be used for
Speaker Interface. A SPKR output is provided with
on/off and volume control logic incorporated in the
modem, requiring only an external amplifier to drive a
Hardware Interface Signals
Figure 1 illustrates the functional interface signals. In
this diagram, an active low signal is indicated by a
forward slash “/” (e.g., /RESET). A clock intended to
activate logic on its rising edge (low-to-high transition)
is called active high (e.g., TDCLK), while a clock
intended to activate logic on its falling edge (high-to-
low transition) is called active low (e.g., /RDCLK).
Figure 2 illustrates the modem pin assignments.
Table 3 provides the signal descriptions.
Power and Maximum Ratings
Table 4 lists the current and power requirements.
Table 5 lists the absolute maximum ratings.
The modem is offered in two configurations depending
upon the selected clock source. One configuration
utilizes a crystal source and the other uses an
For the crystal configuration, the crystal is connected to
XTLI (pin 85) and XTLO (pin 86). For the oscillator
source, the oscillator is connected to CLKIN (pin 85)
and XTLO (pin 86) is not connected.
Figure 3 shows the package dimensions.
Additional design information is described in the
FM336Plus V.34/Group3 High Performance Fax
Modem Designer’s Guide.