ch1786nh ETC-unknow, ch1786nh Datasheet - Page 2

• Manufacturer Part Number: ch1786nh
• Description: Ch1786 Family Ultra Small 2400bps Modems
• Manufacturer: ETC-unknow

Cermetek Microelectronics, Inc.
DESCRIPTION OF FUNCTIONAL BLOCKS
AND DISCUSSION OF BASIC OPERATIONS
Figure 1 contains a functional block drawing of the
CH1786.
function
demodulator, controller, NVRAM and an FCC Part 68
approved and UL 1950/CSA C22.2 950 listed PSTN
line interface.
Modulation/Demodulation and Modem Controller.
These functions are provided by a monolithic modem
integrated circuit.
accommodate integrated AT command control and
contains the necessary resident interfaces for general
communication and routing to the DAA.
Telephone Line Interface or DAA.
family of modems is designed to meet 1500VAC RMS
isolation and provide 2122V peak surge protection.
Consequently, the CH1786 satisfies U.S. FCC Part
68
requirements, and will meet other international
approval agency requirements that specify these
levels of isolation.
With the exception of the U.S., most countries
(including Canada) require submission of the final
product or system containing the CH1786 to the
appropriate governing regulatory agency for approval.
Typically this is accomplished by submitting the final
end product to an independent test house or
consultant for evaluation.
consultant then forwards the test results and
applicable documents to the regulatory agency. Call
Cermetek for a list of suggested consultants.
Non-Volatile RAM (NVRAM). The NVRAM present
on the CH1786 is sufficient to store up to two user
customized modem configurations.
command will store the active modem configuration in
the selected NVRAM locations by specifying an n of 0
or 1.
The
configurations to be automatically recalled and made
active upon a reset or power up.
command immediately recalls and activates a stored
configuration. Refer to Tables 4, 5 and 6 for storable
S-Registers and available commands.
The NVRAM can save up to four telephone numbers
with up to 36 digits or modifiers in each telephone
number. The AT&Zn=s command will store s, the
telephone number dial string. The individual NVRAM
telephone number storage locations are selected by
specifying an n of 0,1,2,or 3.
command will cause the modem to dial the stored
telephone number in location n. NVRAM is not
available on the CH1786LC or CH1786NH.
2003 Cermetek Microelectronics, Inc.
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Page 2
SUPPORT FEATURES
AT Command Set. A 40-character command line is
supported.
may contain standard or enhanced commands. The
commands are compatible with EIA Document
TR302.2/88-08006.
Serial Host Interface. The serial interface is a V.24
(EIA-232) compatible interface. Ten Bits total: 1 start
bit, 1 stop bit, and eight data bits which can be either
eight bits with no parity or seven odd or even with
parity. The start bit is LOW going. RXD and TXD
data is non-inverted. See pin description in Table 2.
Speaker Interface.
receiver analog input and provides a signal that can
be used to monitor call progress. The SPK signal can
drive a 300 Ω load directly. Typically, the SPK signal
is input into an audio power amplifier and the
amplifier, in turn, drives the speaker coil.
speaker is activated with the ATMn command. The
speaker volume is adjusted using the ATLn
command, where n is 0,1,2,or 3. Increasing numbers
correspond to higher volume. Figure 6 indicates one
method of driving an external 8 Ω speaker.
Phone Control. Cermetek ’s CH1786 contains a pin
called Voice or Data (V/D). The V/D pin toggles high
when the modem goes off hook. This pin can be
used to activate a relay which can switch a telephone
on or off the Tip and Ring incoming PSTN lines. This
feature allows any telephone associated with the
CH1786 to be disconnected when a data call is in
progress, thereby preventing the data from being
disturbed by an inadvertent telephone pick-up. See
Figure 2.
Speed and Parity Selection. Prior to call initiation,
the host controller trains the modem to the host
speed (2400,1200 or 300bps) and parity (odd, even,
mark, space, or none) via a host-initiated training
sequence. This training also sets the speed of the
data
automatically adjust to the originator’s speed when
answering calls.
The CH1786 matches the host’s parity when it returns
status messages to the host.
connection, however, the modem passes parity
through without interpretation or alteration.
Sleep Mode. To minimize power consumption, the
CH1786 includes a power down feature called Sleep
Mode.
automatically enter Sleep Mode after 0 to 254
seconds of inactivity. The inactivity delay is selected
using the ATS24 command.
delivered from the factory with a 5 second inactivity
delay enabled (i.e., ATS24=5). The CH1786 returns
to normal operation when a ring signal is received or
for
originate
When
The command line starts with AT and
CH1786 Family of Ultra Small 2400bps Modems
Document No. 607-0004 Revision L1 (06/03)
activated,
The SPK output reflects the
calls.
The
the
The CH1786 is
During a data
CH1786
CH1786
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