ch2056tbr ETC-unknow, ch2056tbr Datasheet - Page 3

• Manufacturer Part Number: ch2056tbr
• Description: High Speed Modem Family
• Manufacturer: ETC-unknow

Cermetek Microelectronics, Inc.
CONNECTING TO THE HOST UART
Since a modem communicates data serially and most
host products handle data in a parallel format, a UART
is needed to make parallel-to-serial and serial-to-
parallel translations.
SUPPORTED FEATURES
AT Command Set. The HS Modem supports the AT
Command set with extensions and can operate with
industry standard communication software. The AT
Commands are compatible with TR302.2/88-08006.
Serial Host Interface.
operates in asynchronous mode and supports a 5V,
RS232- like interface called V.24 (EIA-232-E). The HS
Modem supports a full RS-232C/V.24 serial interface.
Signal levels are TTL rather than RS-232C level
compatible, which allows direct connection of the HS
Modem to the host’s UART without level translating
circuitry.
descriptions.
The modem is controlled by sending serial commands
over TXD and by monitoring serial status messages
returned on RXD. All other serial interface lines may
be utilized for the convenience of a particular
application but are not required by the modem.
Unused outputs from the HS Modem should be left
unconnected.
proper logic level. See Table 3.
Speaker Interface.
receiver analog input and provides a signal that can be
used to monitor call progress. The SPK signal can
drive a 300-ohm load directly.
signal is input into an audio power amplifier and the
amplifier, in turn, drives the speaker coil. The speaker
is activated with the ATM command.
volume is adjusted using the ATLn command; where n
is 0, 1, 2, or 3. Increasing numbers correspond to
higher volume.
driving an external 8-ohm speaker.
Zero Power Mode. If an application calls for zero
power during standby periods, the power may be
switched off using external circuitry and then reapplied
when the HS Modem’s RI pin becomes active. The
HS Modem can thus be powered down to zero.
Referring to Figure 2, the controller activates the relay
switch, supplying power (+5V) to the HS Modem. In
this configuration, the ring signal is used to “wake up”
the HS Modem when the HS Modem is in the power
down state.
The internal structure of the RI pin consists of an open
collector opto transistor with a 30k ohm pull-up through
a blocking diode to 5V. The user should apply his own
pull-up resistor to an active 5V source when the HS
2003 Cermetek Microelectronics, Inc.
See Table 3 for a complete set of pin
Unused inputs should be tied to the
Figure 3 indicates one method of
The SPK output reflects the
The HS Modem family
Typically, the SPK
The speaker
Page 3
Modem is powered down. The internal blocking diode
provides supply isolation.
The pins of the HS Modem will be in an undefined
state when powered is switched off.
taken into consideration to assure that no unwanted
signals are presented to the HS Modem during power
down.
Figure 2. Zero Power Operation.
Power Supply. The HS Modem module is a complex
set of sensitive subsystems.
normal operation, the HS Modem decodes analog
signals from the telephone line that are in the millivolt
range. Steps must be taken by the user to guarantee
that power supply noise on all supply lines, including
ground, does not exceed 25mV peak to peak.
necessary, use dedicated power and ground planes.
Failure to provide such operating conditions could
cause the HS Modem to malfunction or to function
erratically.
The HS Modem family requires +5V ±5% supply. It is
recommended that bypass capacitors be placed on the
power supply as close to the HS Modem’s supply input
pins as practical. It is recommended that a 10 µF or
greater tantalum capacitor in parallel with a 0.1 µF
ceramic capacitor be used.
provide shielding from nearby sources of EMI, such as
relays, motors and other power supplies.
Automatic Speed/Format Sensing. The HS Modem
supports
operation.
The HS Modem can automatically determine the
speed and format of the data sent from the DTE over
the serial interface; and can sense the following broad
range of speeds:
both Command and Data modes of
Document No. 607-0003 Revision K3 (09/03)
High Speed Modem and FAX Family
During the course of
The user must also
This must be
If