r6781-12 Conexant Systems, Inc., r6781-12 Datasheet - Page 42

• Manufacturer Part Number: r6781-12
• Description: Embedded Modem Family
• Manufacturer: Conexant Systems, Inc.

Table 3-5. Hardware Interface Signal Definitions (2 of 5)
3-16
WAKEUP
NVRCS
NVRSK
NVRDIO
SPKR
RXD
TXD
DTR
CTS
DSR
DCD
CI/HS
RI
AAE
MR
Label
DI
DO
DO
DIO
O(DF)
DO
DI
DI
DO
DO
DO
DO
DO
DO
DO
I/O Type
Asynchronous Serial Interface (Serial Interface Only; SEREN = Low)
Serial Indicator Interface (Serial Interface Only; SEREN = Low)
Wake Up. For serial interfaces only, WAKEUP input low removes the modem from the sleep
mode (if in the sleep mode), or prevents the modem from entering the sleep mode (if not in
the sleep mode). WAKEUP high allows the modem to enter sleep mode after 5 seconds of
modem inactivity. WAKEUP is typically connected to DTR or TXD.
NVRAM Chip Select. NVRCS output high enables the NVRAM.
NVRAM Shift Clock. The NVRSK output is used to shift data to or from the NVRAM.
NVRAM Data In/NVRAM Data Out. NVRDIO is a bidirectional signal that carries both the
serial input data from the NVRAM and the serial output data to the NVRAM. Depending on the
specific NVRAM used, a resistor may be required between the NVRAM DO output pin and the
modem NVRDIO bidirectional line. (Refer to
Speaker Analog Output. The SPKR output reflects the output of the receive analog signal.
The SPKR output is turned on or off by the Speaker Control Option (Mn command), and the
gain is controlled by the Speaker Volume Option (Ln command). When the speaker is turned
off, the SPKR output is clamped to the voltage at the VC pin. The SPKR output can drive a
load as low as 300 . Typically, the SPKR output is an input to an external LM386 audio
power amplifier.
Received Data. The modem presents received serial data to the RXD output pin.
Transmitted Data. The modem obtains serial data to be transmitted from the TXD pin.
Data Terminal Ready. DTR input ON (low) indicates that the DTE is ready to operate. DTR
input OFF (high) indicates that the DTE is not ready to operate.
Clear to Send. In data modes, the CTS output is ON; in fax modes, CTS is optionally used for
flow control.
Data Set Ready. The DSR output is controlled by the AT&Sn command.
Data Carrier Detected. The DCD output is controlled by the AT&C command.
Calling Indicator/High Speed Indicator. CI/HS output ON (low) indicates modem connection
at 2400 bps.
Ring Indicator. RI output ON (low) indicates the presence of an ON segment of a ring signal
on the telephone line. (The ring signal cycle is typically 2 seconds ON, 4 seconds OFF.) The
OFF (high) condition of the RI output is maintained during the OFF segment of the ring cycle
(between rings) and at all other times when ringing is not being received.
Auto Answer Enable. AAE output ON (low) indicates that modem auto answer mode has
been enabled with the S0 = command. AAE high indicates auto answer has been disabled.
The AAE output also indicates the status of the RI output.
Modem Ready. MR output ON (low) indicates that the modem is ready; i.e., modem power is
on and a test mode is not selected. In a test mode, the MR output pulses to indicate a test is
in process.
Speaker Interface
NVRAM Interface
Conexant
Signal Name/Description
Figure 3-5
and the NVRAM data sheet.)
EmbeddedModem Family
D224ATLVDSC