CH1786A Family of Ultra Small 2400bps Modems
INTRODUCTION
The CH1786A represents the next generation of full
function, FCC Part 68 approved 2400bps modems in
the CH1786 Family. These modems provide a fast,
easy and flexible way to integrate a modem into any
OEM product while utilizing the minimum amount of
peak surge protection minimum.
PCB space (1.01”x 1.27”x 0.52”).
The CH1786A
family only requires two external interfaces: a ITU-T
V.24 serial interface that can be routed directly to a
UART, and a Tip and Ring interface which goes
directly to an RJ-11 jack for the PSTN line connection.
The CH1786A can be controlled with industry standard
standby mode.
AT commands and, hence, is compatible with
available industry communication software. DTE
speed conversion allows commands and data to be
adaptive
and
fixed
compromise
sent at rates that differ from the modem connection
equalization.
speed.
In most cases, the CH1786A can be used
interchangeably with the CH1786. See Attachment I
for equivalency comparisons and differences by
and telephone numbers.
product.
All
CH1786A
modems
support
asynchronous
operation at 2400bps, 1200bps, and 300bps to both
Bell and ITU-T standards.
The CH1786A also
supports
Fast
Connect
and
LAPM/MNP
Error
Correction.
The resident PSTN line interface, or Data Access
Arrangement (DAA), while being FCC approved, is
also Industry Canada CS-03 Part I Registered.
Further, the CH1786A can be approved in other
countries that require 1500VAC RMS isolation
requirements per UL 1950 Edition 3.
The CH1786A family of modems operate off a single
5-volt supply. The low power operation and automatic
standby mode make these modems ideally suited for
Figure 1. Functional Block Diagram of CH1786A.
portable equipment. In addition, their small physical
size affords maximum flexibility in equipment design.
DESCRIPTION OF FUNCTIONAL BLOCKS
CH1786A comes with FCC Part 68 approval and is
AND DISCUSSION OF BASIC OPERATIONS
shipped from the factory with an FCC Part 68 label
Figure 1 contains a functional block drawing of the
indicating
the
registration
number
and
ringer
CH1786A. The CH1786A is a highly integrated, full-
equivalent. This label should be prominently displayed
function
modem,
comprised
of
a
modulator/
on the end product.
demodulator, controller, NVRAM and an FCC Part 68
approved and UL 1950 Edition 3/CSA C22.2 950 listed
PSTN line interface.
FEATURES
Modulation/Demodulation and Modem Controller.
and Bell 103.
These functions are provided by a monolithic modem
integrated circuit.
This IC has built-in facilities to
US:B46MM07BCHXXXXAYY
accommodate integrated AT command control and
contains the necessary resident interfaces for general
IC:176A-CHXXXXAY
communication and routing to the DAA.
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Document No. 607-0019 Revision A8 (03/06)
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CH1786A Family of Ultra Small 2400bps Modems
Telephone Line Interface or DAA. The CH1786A
SUPPORT FEATURES
AT Command Set. A 50-character command line is
supported. The command line starts with AT and 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.
Figure 2. Voice/ Data Port Control
Speaker Interface.
The SPK output reflects the
receiver analog input and provides a signal that can be
family of modems is designed to meet 1500VAC RMS
used to monitor call progress. The SPK signal can
isolation and provide 2122V peak surge protection.
drive a 300 Ω load directly. Typically, the SPK signal
Consequently, the CH1786A satisfies U.S. FCC Part
is input into an audio power amplifier and the amplifier,
68 and Industry Canada CS-03 Part I requirements,
in turn, drives the speaker coil.
The speaker is
and will meet other international approval agency
activated with the ATMn command.
The speaker
requirements that specify these levels of isolation.
volume is adjusted using the ATLn command, where n
is 0, 1, 2, or 3. Increasing numbers correspond to
With the exception of the U.S., most countries
higher volume.
Figure 5 indicates one method of
(including Canada) require submission of the final
driving an external 8 Ω speaker.
product or system containing the CH1786A to the
appropriate governing regulatory agency for approval.
Phone Control. Cermetek’s CH1786A contains a pin
Typically this is accomplished by submitting the final
called Voice or Data (V/D). The V/D pin toggles high
end product to an independent test house or
when the modem goes off hook. This pin can be used
consultant for evaluation. The test house or consultant
to activate a relay which can switch a telephone on or
then
forwards
the
test
results and
applicable
off the Tip and Ring incoming PSTN lines.
This
documents to the regulatory agency. Call Cermetek
feature allows any telephone associated with the
for a list of suggested consultants.
CH1786A to be disconnected when a data call is in
progress, thereby preventing the data from being
Non-Volatile RAM (NVRAM). The NVRAM present
disturbed by an inadvertent telephone pick-up. See
on the CH1786A is sufficient to store up to two user
Figure 2.
customized modem profile configurations.
The
AT&Wn command will store the active modem
Speed and Parity Selection. Prior to call initiation,
configuration in the selected NVRAM profile by
the host controller trains the modem to the host speed
specifying either an n of 0 or 1. The CH1786A is
(2400, 1200 or 300bps) and parity (odd, even, mark,
delivered with Factory Default setup parameter values
space, or none) via a host-initiated training sequence.
pre-stored in NVRAM profile 0.
This training also sets the speed of the data for
originate calls. The CH1786A will automatically adjust
The
AT&Yn
command
selects
the
modem
to the originator’s speed when answering calls.
configurations to be automatically recalled and made
active upon a reset or power up. The ATZn command
The CH1786A matches the host’s parity when it
immediately recalls and activates a stored profile
returns status messages to the host. During a data
configuration. Refer to Tables 4, 5 and 6 for storable
connection, however, the modem passes parity
S-Registers and available commands.
through without interpretation or alteration.
The NVRAM can save up to four telephone numbers
Sleep Mode. To minimize power consumption, the
with up to 31 digits or modifiers in each telephone
CH1786A includes a power down feature called Sleep
number.
The AT&Zn=s command will store s, the
Mode.
When
activated,
the
CH1786A
will
telephone number dial string. The individual NVRAM
automatically enter Sleep Mode after 1 to 255 seconds
telephone number storage locations are selected by
of inactivity. The inactivity delay is selected using the
specifying an n of 0, 1, 2, or 3.
The ATDTS=n
ATS24 command and defaults to 0 which will disable
command will cause the modem to dial the stored
this feature.
The CH1786A returns to normal
telephone number in location n.
operation when a ring signal is received or upon an
input low signal on the TXD pin. A SLEEP output
signal is available to control power to external devices.
2006 Cermetek Microelectronics, Inc.
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Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
In Figure 5, a FET controlled by the SLEEP signal
found
on
the
Cermetek
web
site
located
at
turns off the external speaker amplifier when the
http://www.cermetek.com.
CH1786A enters Sleep Mode. In Sleep Mode, power
is reduced to about 1/3 of normal operating power.
Answer Tone. A ITU-T (2100 Hz) or Bell (2225Hz)
answer tone is generated depending on the selected
Zero Power Mode. The “P” versions of the CH1786A
configuration.
Refer to “AT Commands and S-
Family supports Zero Power Mode operation. If an
Registers” for a more detailed discussion.
application calls for zero power during standby
periods, this feature allows the power to the CH1786A
Data Encoding. The data encoding conforms to ITU-
to be switched off using external circuitry and then
T recommendations V.22bis or V.22, or Bell212A, or
reapplied when the CH1786A’s RI pin becomes active.
103, depending on the selected configuration. Refer
The CH1786A can thus be powered down to zero.
to “AT Commands and S-Register” for a more detailed
discussion.
Referring to Figure 3, the controller activates the relay
switch, supplying power (+5V) to the CH1786A. In this
Line Equalization. Transmitter and receiver digital
configuration, the ring signal is used to “wake up” the
filters compensate for delay and amplitude distortion
CH1786A when the CH1786A is in the zero power
during operation on nominal phone lines. In addition,
state.
automatic adaptive equalization in the receiver
minimizes the effects of inter symbol interference.
Transmission Speed.
In normal operation, the
originating modem initiates the call and attempts to
connect to the answering modem at a speed
established by the originating modem’s controller prior
to call initiation.
This is referred to as the Initial
CH1786A-P
Trained Rate. Upon receiving the call, the answering
modem will attempt to connect to the originating
modem at its Initial Trained Rate. If these two rates
are identical, the connection is made. If the speeds
differ, the answering modem must adjust its rate or
terminate the call. Table 1 indicates the connection
rate when the calling modem’s Initial Trained Rate and
answering modem’s Trained Rate are different.
Error Correction. The CH1786A supports LAPM and
MNP error correction. Error correction is enabled via
the \Nn command. Enabling error correction overrides
&Qn and sets S36 and S48 values.
Refer to
Cermetek, “AT Commands and S-Registers”, for a
Figure 3. Zero Power Operation.
more detailed discussion.
As indicated in Figure 2, the user connects an external
Table 1. Connection Rates.
pull-up resistor (Cermetek recommends 30k ohms) to
Connection Rate Resulting
an active 5V source thereby providing a small current
Answering Modem
When Calling Modem Initial
to the CH1786A through the RI pin when the CH1786A
Initial Trained Rate
Rate Is:
is powered down (i.e., no power applied to the VCC
300
1200
2400
pin).
An internal blocking diode provides supply
isolation.
300
300
1200
1200
1200
300
1200
1200
The pins of the CH1786A will be in an undefined state
when powered is switched off. This must be taken into
2400
300
1200
2400
consideration to assure that no unwanted signals are
presented to the CH1786A during power down.
NOTE
A 2400-baud connection rate will only result if both
Guard Tone. A guard tone of 550 Hz or 1800 Hz can
modems are initially set at 2400 baud.
be generated at 6 dB or 9 dB below the transmit level,
respectively, by using the &Gn command. For a more
detailed discussion, refer to Cermetek Document 613-
Ring Indicator (RI). The RI pin follows the frequency
0001, “AT Commands and S-Registers”, which can be
of the ring signal and toggles low when the CH1786A
detects an incoming call. The ring signal is typically 20
to 30 Hz and is on for 2 seconds and off for 4 seconds.
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CH1786A Family of Ultra Small 2400bps Modems
Although not TTL compliant, the RI pin can,
schematic indicating one possible configuration for
nonetheless, be utilized to activate external circuitry
voice/ tone utilization.
including the external RST pin.
Typically, voice communication would precede data
+MS Command.
The user may override the
communications.
For this case, the following
automatic data rate function of the HS modems. This
commands should be used to configure the CH1786A
is accomplished by executing the +MS command.
(Refer to Figure 4):
This command allows the user to specify the desired
data modulation protocol. Further, the +MS command
Enter: ATS0=0<CR>
Disables auto-answer
may be used to force a desired data rate and/or
Result: OK
restrict the allowed data rate.
The supported
modulation schemes are listed above.
Enter: ATS7=255<CR>
Disables data-carrier time
Result: OK
out
The
following
examples
establish
the
V.22bis
modulation scheme:
Enter: ATS10=255<CR> Disables lost-carrier time
Result: OK
out
Enter:
AT+MS=V22B
Result:
OK
WARNING
This is identical to the following explicit +MS
The CH1786A has been FCC Part 68 and Industry
command:
Canada CS-03 Part I approved as a data modem
only.
Utilization of the Voice/DTMF Tone Port
Enter:
AT+MS=V22B,0,300,1200,300,1200
requires further registration.
FCC and Industry
Result:
OK
Canada will require that the system, including the
CH1786A and the handset or DTMF transceiver,
adhere to Part 68 and CS-03 Part I rules.
NOTE
The minimum transmission rate is not stored and will
default to 300bps upon execution of reset or upon
The
following
command
sequences
illustrate
power up.
implementation
of
common
Voice/Tone
Port
applications.
Refer to, “AT Commands and S-Registers”, for a more
1. To answer a voice call.
detailed discussion of the +MS command.
(a) Enter: ATH1<CR>
Result: OK
Power Supply. The CH1786A modem module is a
(b) Drive V.INJ. HIGH to activate relay.
complex set of sub-systems.
During the course of
(c) Begin voice conversation.
normal operation the CH1786A decodes analog
signals from the telephone line that are in the millivolt
2. To switch to data mode.
range. Steps must be taken by the user to guarantee
(a) Drive V.INJ. LOW
that power supply noise on all supply lines, including
(b) At the originate modem:
ground, does not exceed 50 mV peak to peak. Any
Enter: ATX1<CR>
frequency between 20 kHz and 150 kHz must be less
Result: OK
than 500 micro volts peak.
If necessary, use
dedicated power and ground planes.
Failure to
3. To disconnect (hang-up) a voice call or a data call.
provide such operating conditions could cause the
(a) Enter: ATH<CR>
CH1786A to malfunction or to function erratically.
Result: OK
The CH1786A requires a single +5V ±5% supply. It is
4. Place a call to 1234567 using the CH1786A’s
recommended that by-pass capacitors be placed on
DTMF tone generator, then use VOICE mode for
the power supply as close to the modem’s supply input
voice communications.
Note that the CO
as practical.
It’s recommended a 10 µ F Tantalum
command disables carrier generation.
capacitor in parallel with a 0.01 µF ceramic capacitor
(a) Enter: ATDT1234567;C0<CR>
be used.
Result: OK
(b) Drive V.INJ. HIGH
Voice/DTMF Tone Injection Port.
The CH1786A
provides two pins to allow the user to share the
telephone line interface associated with the modem for
MODEM CONTROL
voice and DTMF applications.
Figure 4 contains a
The CH1786A modem may be controlled by sending
serial ASCII command sequences. The commands
2006 Cermetek Microelectronics, Inc.
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CH1786A Family of Ultra Small 2400bps Modems
are sent to the modem serially on the TXD pin. After
Training the Modem. Each modem must be trained
execution of a received command, the modem returns
to match its host’s speed and parity so that it is able to
a serial status message that can be read on pin RXD.
recognize serial asynchronous commands sent to it by
This message indicates command completion status.
the host’s is UART. The host must retrain the modem
Refer to Table 3 for a complete list of status
each time a reset pulse is applied on RST or after a
messages.
RESET serial command has been issued.
Modem Training Command Sequence.
The
CH1786A is trained by sending it the following
sequence:
Enter: AT<CR>
Result: OK
Where: A and T may be either upper or lower case but
must be the same case.
<CR> represents carriage return
The AT sequence is referred to as an attention
sequence. The CH1786A will respond with one of the
following status messages, depending on whether it is
optioned for Terse (abbreviated) or Verbose (English)
status messages.
Figure 4. Voice/Tone Injection.
Result: 0<CR> (Terse)
or
Result:
<CR><LF>OK<CR><LF> (Verbose)
IMPORTANT NOTE
Where:
<CR> represents carriage return (ASCII 13
Although every effort has been made to design the
or HEX 0D).
CH1786A products to be fully and completely
<LF> represents line feed (ASCII 10 or HEX
compatible with the existing CH1786 family, there are
0A).
some minor differences.
Refer to Table 14 for
equivalency information and refer to Attachment I for
After responding with an OK, the CH1786A is in idle
a summary of product differences.
mode and is ready to accept additional commands.
An alternate attention sequence A/ may be sent which
behaves much like the AT sequence except that it
INITIALIZING THE MODEM
causes the previously entered command specified with
Before commands may be sent to the CH1786A, the
an AT prefix to be executed. When given, both the AT
CH1786A must be initialized. Initialization is a two
and A/ must be in upper case ASCII. No carriage
step activity consisting of:
return is needed for the A/ command.
1. Hard Reset. This is accomplished by applying a
hardware reset pulse to pin RST or by switching
THE COMMAND FORMAT
the power off and then back on.
Typical commands consist of three elements: the
attention sequence, the commands themselves, and a
2. Initial modem training.
The CH1786A must be
terminating carriage return.
trained to the host’s speed and parity (odd, even,
mark, space or none).
AT[commands]<CR>.
These activities are briefly described below.
Where: AT represents attention sequence.
[Commands] represents command strings.
Reset. Upon applying power to the CH1786A, the
<CR> represents carriage return (ASCII 13 or
CH1786A automatically generates an internal reset
HEX 0D).
pulse. The user may also reset the modem externally
by applying a high-going reset pulse to the RST pin for
When entering commands to the modem, the
at least 10ms after the +5V power supply has
backspace character-control-H (ASCII 8 or HEX 08)
stabilized. Delay sending commands to CH1786A for
may be used to edit mistakes. AT and A/ may not be
200ms after reset has been initiated to allow the
edited.
Multiple commands may be placed in the
CH1786A time to properly reconfigure.
command line. A command line may be as long as 40
characters, excluding the letters AT .
By way of
example, the command below instructs the CH1786A
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CH1786A Family of Ultra Small 2400bps Modems
to configure itself to not echo characters when in
AT COMMAND APPLICATIONS
command mode E0 and then put itself in answer mode
Dialing A Phone Number. The Dial command takes
A .
the form Dn , where n is a string of characters. In the
Enter: ATE0A<CR>
simplest form, n will be only the digits of the phone
Result: OK
number to be dialed.
AT Command Set. The available command set is
Example: Dial number.
divided into four types of commands: dial modifiers,
Enter:
ATD1234567<CR>
basic commands, ampersand and percent commands.
Result:
OK
Refer to the complete list in Table 5.
In response to this command, the CH1786A dials the
AT Command Data Rate. With the serial interface,
telephone number “123-4567” and then waits for a
the rate is speed sensed for parity and format.
carrier from the distant modem.
If no carrier is
detected within a given time (the default time is 30
seconds), the CH1786A automatically releases the line
THE STATUS MESSAGES
and sends a NO CARRIER result code. If a carrier is
The CH1786A responds with a status message after
detected, the CH1786A gives a CONNECT result code
each command is executed.
This status message
and goes on-line, permitting communication with the
may either be a numeric code (Terse Result Code)
distant modem.
followed by a carriage return; or a carriage return and
line feed with a message in English (Verbose Result
The Dial Command may also be issued without a
Code) followed by a carriage return and line feed.
telephone number. ATD causes the modem to pick up
the telephone line without dialing a number.
Various status code subsets are enabled with the Xn
command. Where n=0, 1, 2, 3, 4 establishes the result
Pause During Dialing. When placing a call from an
codes allowed to be sent from the CH1786A to the
office with a telephone connected to a PBX, it may be
DTE.
necessary to dial an access code (usually the digit 9)
to get an outside line.
Inserting a comma in the
telephone number instructs the modem to pause for a
NOTE
specific length of time. The factory set default pause
The CH1786A is factory set to X4, which allows all
time is 2 seconds.
result codes.
Example: Dial 9,pause, dial number.
Enter:
ATDT9,1234567<CR>
MODEM STATES
Result:
OK
The CH1786A can be in either command mode or data
Multiple commas may be used to generate integer
mode. When the modem is idle, it is in command
multiples of the specified delay time.
mode by default and will recognize commands. When
data transmission is in progress, the CH1786A is in
Originate a Call in Answer Mode. The D command
the data mode state and will not recognize commands.
forces the modem into originate mode.
To call an
To force the CH1786A to recognize commands, the
originate-only modem, dial the number and set the
host must send an escape sequence to the CH1786A
modem to answer mode via the R command (reverse
forcing it out of data mode and into command mode.
originate). This is done by including an R at the end of
the telephone number.
The escape sequence consists of a “guard time” (a
period where no characters are sent to the modem),
Example: Change modem from original-only to answer
followed by 3 escape characters, followed by another
mode.
guard time. The guard time is set by register S12.
Enter:
ATDT1234567R<CR>
The escape character code is set in register S2. At
Result:
OK
power-up, the guard time is set to 1 second minimum,
and the escape character is set as “+.” There is no
Multiple commas may be used to generate integer
minimum delay between characters but the maximum
multiples of the specified delay time.
delay is set by register S12.
Redial Last Number.
The repeat command is a
The CH1786A will stay off-hook with its carrier on after
convenient way to execute the previously entered
the escape sequence is received. It will return an OK
command line.
status message when it is ready to accept commands.
The CH1786A may be put into data mode by issuing
Example: Use A/ , the repeat command, to redial the
the command ATO<CR> .
last telephone number dialed.
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CH1786A Family of Ultra Small 2400bps Modems
Enter:
A/
(telephone
number).
ASCII
data
is
Result:
ATDT1234567R<CR> Previous command
presented.
OK
line executed
2
Enables
Caller
ID
with
unformatted
Return to Command State.
Use ; to return to
presentation to the DTE.
The data is
command mode offer dialing.
presented
in
a
continuous
string.
Example: Touch-tone dial 9, pause, dial number,
HEXADECIMAL data is presented.
return to Command.
Enter:
ATDT9,1234567;<CR>
Refer to Application Note # 174, Caller ID Feature For
Result:
OK
CH1786A, CH179XA and CH2056A Modems, for
additional information and examples.
V.22 Fast Connect.
The CH1786A supports non-
standard V.22 fast connect protocols.
This feature
The AT+VRID command affects the format of the data
reduces the connect time to 3-4 seconds. However, to
provided by the PSTN Caller ID services for the last
utilize the fast connect protocol, this protocol must be
received call. The DTE is presented this data once
supported by both modems. Further, the DCE speed
every time the +VRID command is executed.
must be set to 1200 baud (i.e., V.22).
Enter: AT+VRID=n<CR>
To setup the CH1786A to connect utilizing Fast
Result: Data Stream from most recent call
Connect, execute the following commands:
Where n is a decimal number corresponding to the
Enter: AT+MS=V22,0,300,1200,300,1200<CR>
selected option as described below.
Result: OK
0
Reports
Caller
ID
with
formatted
Enter: $F2<CR>
presentation to the DTE.
The data is
Result: OK
presented the data items in a <Parameter
This forces the CH1786A to communicate using the
Description> <Value> pair format.
The
V.22 protocol and to attempt to connect using Fast
expected pairs are: date, time, name, and
Connect. If Fast Connect is not supported by the other
caller code (telephone number).
modem, the CH1786A will connect using the standard
V.22 protocol.
1
Reports
Caller
ID
with
unformatted
presentation to the DTE.
Caller ID (CID). The “C” versions of the CH1786A
Family supports Caller ID.
The +VCID command
Refer to Application Note # 174, Caller ID Feature For
controls reporting and presentation of the data
CH1786A, CH179XA and CH2056A Modems, for
provided by the PSTN Caller ID services.
Data is
additional information and examples.
presented to the DTE between the first and the second
ring indication. This command affects the data format
IMPORTANT NOTE
for incoming calls as the call is being received.
Caller ID (CID) requires that the PSTN service
provider supply the required data.
The Caller ID
Enter:
AT+VCID=n&W0&W1<CR>
feature will report the NULL string if the CID service
Result:
OK<CR><LF>
is not activated by the PSTN service provider.
IMPORTANT NOTE
Automatic Answering. The S0 register controls the
The &W0 (or &W1 ) command, as appropriate per
number of rings that must occur before the CH1786A
the specification of &Y0 (or &Y1 ), must be executed
answers a incoming call. The register may range in
before the +VCID command will be implemented by
value from 0 to 255.
the CH1786A.
To set the CH1786A to not answer any incoming calls,
Where n is a decimal number corresponding to the
executed the following command:
selected option as described below.
Enter:
ATS0=0<CR>
0
Disable Caller ID reporting. (Default.)
Response OK
1
Enables
Caller
ID
with
formatted
When S0 is set to 0, the modem will not auto-answer.
presentation to the DTE.
The data
To set the CH1786A to answer after 3 rings, execute
presented is in a <Parameter Description>
the following command:
<Value> pair format.
The expected pairs
are: date, time, name, and caller code
Enter:
ATS0=3<CR>
Response OK
2006 Cermetek Microelectronics, Inc.
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CH1786A Family of Ultra Small 2400bps Modems
Figure 5.
CH1786A block diagram illustrating typical feature implementations: V/D control, RJ-11
connection, speaker for call progress monitoring, serial port connection, external reset, +5V and GND.
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Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 2. CH1786A Pin Descriptions
PIN
NAME
TYPE
FUNCTION
1
RING
I/O
RING . Directly connects to the telephone line’s Ring lead through a user supplied
RJ-11C jack.
2
TIP
I/O
TIP . Directly connects to the telephone line’s Tip lead through a user supplied RJ-
11C jack.
3
RXA
O
ANALOG VOICE INJECTED . Receive Signal. Let float if not used.
4
TXA
I
ANALOG VOICE INJECTED . Transmit Signal. Let float if not used
5
SPK
O
SPEAKER . Audio output for speaker. See speaker control schematic in Figure 5.
6
NC
-
No connection.
7
NC
-
No connection.
8
SLEEP
O
SLEEP . Active LOW. A LOW indicates CH1786A is in low power idle mode. Used
to control power to other devices. See Figure 5. Register S24 is the sleep timer
register. When the CH1786A is inactive for a period of time specified by S24, the
CH1786A will power down by about 1/3 of its normal operating power. During
power down, all I/O lines become undefined. Default is (ATS24=0) disabled.
9
NC
-
No connection.
10
TXD
I
TRANSMIT DATA . Active Low. Serial Transmit data input. Marking or a binary 1
condition is transmitted when a HIGH is asserted.
11
RXD
O
RECEIVE DATA . Active Low. Serial Receive data output. Received marking or
binary 1 condition is indicated by HIGH.
12
V/D
O
VOICE/DATA . Used to switch between telephone and modem line use. In a typical
application, V/D active HIGH opens the normally closed voice injection relay and
disconnects the handset from the telephone line. HIGH indicates the CH1786A is
off-hook and online. Therefore, this pin also reflects the state of the off-hook relay
of the CH1786A. See Figure 2. Let float if not used.
13
DTR
I
DATA TERMINAL READY . Active LOW. Switching off DTR can either return
modem to command state, disconnect phone call, or reset modem. DTR should be
set LOW when not used.
14
DSR
O
DATA SET READY . Active LOW. LOW indicates handshaking with a remote
modem is in progress, and/ or the data carrier of a remote modem has been
detected.
15
RI
O
RING INDICATION. This signal follows the frequency of the ringing signal and is
normally about 20 to 40 Hz for 2 seconds on with 4 seconds off. This pin is also
used for Zero Power option. See Figure 3.
16
CTS
O
CLEAR-TO SEND . Active LOW. Used for hardware Flow Control of data.
17
DCD
O
DATA CARRIER DETECT . Active LOW. LOW indicates a data carrier from a
remote modem is detected. Must be enabled using the &C1 command.
18
NC
-
No Connection.
19
VCC
-
POWER SUPPLY . 5 volts + 5%
20
GND
-
GROUND . Note: Noise should be less than 50mV peak to peak.
21
RST
I
RESET . Active HIGH. This input must be asserted HIGH for at least 10 ms to reset
the modem. RESET is then returned LOW for normal operation. If no system reset
is available, let this pin float. Input impedance of driving circuit should be <10K.
22
NC
I
No Connection.
2006 Cermetek Microelectronics, Inc.
Page 9
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 3. S-Register Summary.
Firmware
Factory
Register
Function
Range
Units
Saved
Defaults
Defaults
S0
Rings to Auto-Answer
0-255
rings
*
000
001
S1
Ring Counter
0-255
rings
000
000
S2
Escape Character
0-255
ASCII
*
043
043
S3
Carriage Return Character
0-127
ASCII
013
013
S4
Line Feed Character
0-127
ASCII
010
010
S5
Backspace Character
0-255
ASCII
008
008
S6
Wait Time before Dial Tone or Blind Dialing
2-255
s
*
002
002
S7
Wait Time for Carrier, Silence or Dial Tone
1-255
s
*
050
050
S8
Pause Time for Dial Delay Modifier
2-255
s
*
002
002
S9
Carrier Detect Response Time
1-255
0.1s
*
006
006
S10
Carrier Loss Disconnect Delay
1-255
0.1s
*
014
014
S11
DTMF Tone Duration
50-255
0.001s
*
085
085
S12
Escape Prompt Delay
0-255
0.02s
*
050
050
S13
Reserved
-
-
000
000
S14
General Bit Mapped Options Status
-
-
*
146 (92H)
146 (92H)
S15
Reserved
-
-
000
000
S16
Test Mode Bit Mapped Options Status (&T)
-
-
000
000
S17
POS Option
-
-
000
000
S19
Reserved
-
-
000
000
S20
Reserved
-
-
000
000
S21
V.24/General Bit Mapped Options Status
-
-
052 (34H)
100 (74H)
S22
Speaker/Results Bit Mapped Options Status
-
-
117 (75H)
117 (75H)
S23
General Bit Mapped Options Status
-
000
000
S24
Sleep Inactivity Timer
0-255
s
000
000
S25
Delay to DTR off
0-255
0.01s
005
005
S26
RTS-to-CTS Delay
0-255
0.01s
001
001
S27
General Bit Mapped Options Status
-
-
073 (49H)
074 (4AH)
S28
General Bit Mapped Options Status
-
-
000
000
S29
Flash Dial Modifier
0-255
0.01s
070
070
S30
Disconnect Inactivity Timer
0-255
10ms
000
000
S31
General Bit Mapped Options Status
-
-
192 (C0H)
192 (C0H)
S36
LAPM Failure Control
-
-
*
007
007
S37
Line Connection Speed
-
-
000
000
S38
Delay Before Forced Hang-up
0-255
s
020
020
S39
Flow Control Bit Mapped Options Status
-
-
003
003
S40
General Bit Mapped Options Status
-
-
*
104 (68H)
104 (68H)
S41
General Bit Mapped Options Status
-
-
*
195 (C3H)
192 (C0H)
S43-S45
Reserved
-
-
-
-
S46
Data Compression Control
-
-
*
138
136
S48
V.42 Negotiation Control
-
-
007
007
S82
LAPM Break Control
-
-
000
000
S86
Call Failure Reason Code
0-26
-
021
021
S91
PSTN Transmit Attenuation Level
0-15
dBm
011
011
S92
FAX Transmit Attenuation Level
0-15
dBm
011
011
S95
Result Code Messages Control
-
-
*
000
000
S210
V.34 Symbol Rate
0-255
-
141 (8CH)
141 (8CH)
NOTES:
1. Parameters indicated with a (*) in the Saved column may be stored in User Profile n=0, 1 by executing
the appropriate &Wn command.
2. A stored Profile is a subset of allowed parameters and is comprised of those parameters displayed
with the &V command.
3. Factory Default values that are different from the Firmware Default values are highlighted in BOLD .
4. Restore Factory Default values using Zn command.
5. Restore Firmware Default values using &Fn command
2006 Cermetek Microelectronics, Inc.
Page 10
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 4. Extended Result Code Summary.
Table 4.
Extended Result Code Summary
Result Code Form
n is ATXn
(Continuation).
Command
Result Code Form
n is ATXn
Terse
Verbose or Long
0
1
2
3
4
Command
or
Terse
Verbose or Long
0
1
2
3
4
Short
or
+F4
+FCERROR
X X X X X
Short
0
OK
X X X X X
80
+ER: ALT
X
X
X
X
X
1
CONNECT
X X X X X
81
+ER: ALT-CELLULAR
X
X
X
X
X
2
RING
X X X X X
83
LINE IN USE
X
X
X
X
X
3
NO CARRIER
X X X X X
85
OFF-HOOK
X
X
X
X
X
4
ERROR
X X X X X
INTRUSION
5
CONNECT 1200
1
X X X X
86
LINE
REVERSAL
X
X
X
X
X
6
NO DIAL TONE
3
3
X X X
DETECTED
7
BUSY
3
3
3
X X
87
NO LINE
X
X
X
X
X
8
NO ANSWER
X X X X X
91
CONNECT 31200
9
CONNECT 0600
1
X X X X
130
+ILRR
X
X
X
X
X
10
CONNECT 2400
1
X X X X
134
+MCR: B103
X
X
X
X
X
11
CONNECT 4800
1
X X X X
135
+MCR: B212
X
X
X
X
X
12
CONNECT 9600
1
X X X X
136
+MCR: V21
X
X
X
X
X
13
CONNECT 7200
1
X X X X
137
+MCR: V22
X
X
X
X
X
14
CONNECT 12000
1
X X X X
138
+MCR: V22B
X
X
X
X
X
15
CONNECT 14400
1
X X X X
139
+MCR: V23
X
X
X
X
X
16
CONNECT 19200
1
X X X X
139
+MCR: V23C
X
X
X
X
X
17
CONNECT 38400
1
X X X X
140
+MCR: V32
X
X
X
X
X
18
CONNECT 57600
1
X X X X
141
+MCR: V32B
X
X
X
X
X
19
CONNECT 115200
1
X X X X
210
+MRR: 25333
X
X
X
X
X
20
CONNECT 230400
X X X X X
211
+MRR: 26667
X
X
X
X
X
22
CONNECT
1
X X X X
212
+MRR: 25333
X
X
X
X
X
75TX/1200RX
213
+MRR: 22666
X
X
X
X
X
23
CONNECT
1
X X X X
214
DIGITAL
LINE
X
X
X
X
X
1200TX/75RX
DETECTED
24
DELAYED
4
4
4
4
X
25
MESSAGE-WAITING
X X X X X
IMPORTANT NOTE
32
BLACKLISTED
4
4
4
4
X
An “X” in a column indicates that the message
33
FAX
X X X X X
(either the long form if verbose, or the value only
35
DATA
X X X X X
for short form) will be generated when that
39
+MRR: 75
X X X X X
particular value of “n” (shown at the top of the
40
+MRR: 300
X X X X X
column) has been selected by the use of ATXn . A
42
+MRR: 600
X X X X X
numeral indicates which less explicit message
44
+MRR: 1200/75
X X X X X
(verbose or short form) will be output for that X
45
+MRR: 75/1200
X X X X X
option.
46
+MRR: 1200
X X X X X
47
+MRR: 2400
X X X X X
48
+MRR: 4800
X X X X X
The Serial Interface Lines. The CH1786A supports a
49
+MRR: 7200
X X X X X
full EIA-232E/V.24 serial interface. Signal levels are
50
+MRR: 9600
X X X X X
TTL rather than EIA-232E level compatible, which
51
+MRR: 12000
X X X X X
allows direct connection of the CH1786A to the host
52
+MRR: 14400
X X X X X
UART without the need for level translation circuitry.
66
+DR: ALT
X X X X X
See Table 2 for a complete pin description.
The
67
+DR: V42B
X X X X X
CH1786A is controlled by sending it serial commands
68
+DR: V44
X X X X X
over TXD and it’s status determined by monitoring the
69
+DR: None
X X X X X
serial status messages returned on
70
+ER: NONE
X X X X X
RXD. DTR is optionally used to reset, terminate calls
77
+ER: LAPM
X X X X X
or return CH1786A to command mode.
All other serial interface lines may be utilized for the
convenience of a particular application but are not
2006 Cermetek Microelectronics, Inc.
Page 11
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 5. AT Command Summary.
Table 5. AT Command Summary (Continuation).
Command Function
Command
Function
A/
Re-execute command
&D0
Modem ignores DTR
A
Go off-hook and attempt to answer call
&D1
Modem assumes command state
B0
Select CCITT connection at 300 or
&D2
Modem
hangs
up,
assumes
1200bps
command state and disables auto-
B1
Sect Bell connection at 300 or 1200bps
answer
Dn
Dial modifier where n is one or more of
&D3
Modem assumes initialization state
the following:
&F0
Restore Factory configuration 0
P
Pulse Dial
&F1
Restore Factory configuration 1
T
Touch Tone Dial
&G0, 1, 2
Guard Tone Options
W
Wait for Dial Tone
&K0
Disable DTE/DCE flow control
;
Return to Command State
&K1,2
Not Supported
@
Wait for Quiet Answer Command
&K3
Enable RTS/CTS DTE/DCE flow
!
Flash Hook
control
,
Pause
&K4
Enable XON/XOFF DTE/DCE flow
0-9/ABCD Dial Digits/Characters & wait
control
for credit card dial tone
&K5
Enable transparent XON/XOFF flow
^
Toggles calling tone
control
L
Redial last number
&P0, 1, 2, 3
Make to Break Ratio Options
*,#
Star digit – tone dialing
&Q0
Select direct asynchronous mode
S=n
Dial the number and store in
&Q1,2,3,4
Not Supported
Directory, n= 0 to 3
&Q5
Modem negotiates an error corrected
E0
Disable command echo
link
E1
Enable command echo
&R0
CTS tracks RTS
H, H0
Initiate a hang-up sequence
&R1
CTS always on
H1
If on-hook, go off-hook and enter
&S0
DSR always on
command mode
&S1
DSR
active
after
answer
tone
L0
Set low speaker volume
detected and inactive after loss of
L1
Set low speaker volume
carrier
L2
Set medium speaker volume
&T0
Terminate Loopback Test
L3
Set high speaker volume
&T1
Initiate Loopback Test
M0
Speaker off
\Bn
Send break of n x 100 msec (n=0 to
M1
Speaker on during hand shaking and
9)
speaker off while receiving carrier
\N0
Select normal speed buffered mode
M2
Speaker on during hand shaking and
\N1
Select direct mode
while receiving carrier
\N2
Select reliable mode
M3
Speaker off during dialing and receiving
\N3
Select auto reliable mode
carrier
and
speaker
on
during
answering
\N4
Force LAPM mode
O0
Go on-line
\N5
Force MNP mode
O1
Go
on-line
and
initiate
a
retrain
\V0
Connect messages are controlled by
sequence
the command settings X, W, and
S95
Sn
Select S Register n
\V1
Connect messages are displayed in
Sn=m
Write value m to S Register n
the single line format
Sn?
Read the value of S Register n
MODULATION COMMANDS
?
Returns Last addressed S Register
+MS
Select modulation
value
V0
Short Form Result Code Option
+MCR=n
Carrier protocol n reporting
V1
Long Form Result Code Option
+MR=n
Select
extended
Modulation
X1, X2,
Result Code Reporting Options
Reporting of +MCR and +MRR to
X3, X4
DTE
+++
Escape Code Sequence
+MRR=m, n
Report Transmit m and Receive n
Z0, Z1
The
modem
performs
soft
reset.
DCE rates to DTE
Restore stored profile 0 or 1 after reset
CALLER ID COMMANDS
&C0
Force DCD active regardless of the
+VCID
Select data presentation format n (0-
carrier state
2) for incoming calls.
&C1
DCD to follow the carrier state
2006 Cermetek Microelectronics, Inc.
Page 12
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 5. AT Command Summary (Continuation).
Fax Modes. The CH1786A Product Family supports
Command
Function
Send and Receive FAX. The modes and rates are
+VRID
Select data presentation format n (0-
determined by the AT+F commands. Refer to Table
1)
for
most
recently
received
6A.
incoming call.
ERROR CORRECTING COMMANDS
FAX modem processing is explicitly defined in ITU-
%C0
Disable data compression
TV.29,
ITU-TV.27,
ITU-TV.21
and
ITU-T
V.17
%C1
Enable MNP 5 data compression
recommendations.
All
modulation,
wave-form
spectrum, and data processing functions conform to
%C2
Enable V.42bis data compression
the appropriate specifications.
%C3
Enable both V.42bis and MNP 5
compression
STORED PROFILE COMMANDS
PHONE LINE CONNECTION GUIDELINES
&V
Display current configuration
1. The CH1786A must be mounted in the final
&W0
Store the active profile in NVRAM
assembly such that it is isolated from exposure to
profile 0
any hazardous voltages within the assembly.
&W1
Store the active profile in NVRAM
Adequate separation and restraint of cables and
profile 1
cords must be provided.
&Y0
Recall stored profile 0 upon power
up
2. The circuitry from the CH1786A to the telephone
&Y1
Recall stored profile 1 upon power
line interface must be provided in wiring that
up
carries
no
other
circuitry
other
than
that
&Zn=x
Store dial string x (31 digits max) to
specifically allowed in the FCC rules (such as A
location n (0-3)
and A1 leads).
MNP10 COMMANDS
-K0
Disable MNP 10 extended services
3. Connection to phone line should be made through
-K1
Disable MNP 10 extended services
an RJ-11C jack.
-K2
Disable MNP 10 extended services
FAX COMMANDS
4. PCB traces from the modem’s RING and TIP pins
+FCLASS=n
Service Class
to the RJ-11C jack must be 0.1 inch spacing or
+F<cmd>?
Report
active
configuration
for
greater to one another and 0.2 inch spacing or
specified command cmd
greater to all other traces. The traces should have
+F<cmd>=?
Report
capabilitied
for
specified
a nominal width of 0.020 inches or greater.
command cmd
+FAA=n
Data/Fax Auto Answer
5. The RING and TIP PCB traces should be as short
+FLO
Flow Control
as possible and oriented to prevent coupling other
+FMI?
Report Manufacturer ID
high speed or high frequency signals present on
+FMM?
Report Model ID
the host circuit PCB.
+FMR?
Report Revisions ID
+FRM=n
Receive Data with n protocol
6. No additional circuitry other than that shown in
+FTM=n
Transmit Data with n protocol
Figure 6 may be connected between the modem
+FRH=n
Receive Data with HDLC Framing
module and the RJ-11C jack.
Doing so will
with n protocol
invalidate the FCC approval.
+FTH=n
Transmit Data with HDLC Framing
7. Surge protection is provided internally. (See
with n protocol
Figure 6). This is mandatory to maintain FCC Part
+FTS=n
Stop Transmission and Wait
68 conveyed approval.
FAST CONNECT COMMANDS
$F0
Normal connection (Default)
8. The CH1786A, the RJ-11C jack, the interfacing
$F1,3,4
Not Supported
circuitry and all PCB traces in between, must be
$F2
V.22 Fast Connect
contained on a PCB with a 94 V-0 flammability
IDENTIFICATION COMMANDS
rating.
I0
Reports product code
I3
Reports firmware Identification code
9. The supplied FCC registration label must be
applied visibly on the outside of the product.
required by the CH1786A depending on user’s
10. The product’s User Manual must provide the user
initialization string.
Unused outputs (from modem)
with instructions for connection and use as
should be left unconnected. Unused inputs should be
recommended in the FCC Registration Section
set to the proper logic level. See Table 2.
below.
2006 Cermetek Microelectronics, Inc.
Page 13
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
CH1786A HANDLING AND ASSEMBLY
notice is recommended and should be included in the
RECOMMENDATIONS
end product’s user manual.
The CH1786A contains static-sensitive components
and should only be handled by personnel and in areas
that are properly protected against static discharge.
FOR YOUR USER’S MANUAL
The two recommended mounting techniques for
The FCC Part 68 rules require the following (or
physically connecting the CH1786A to a PCB are
equivalent) be provided to the end user of equipment
discussed below.
containing a DAA.
Direct Soldering.
The CH1786A may be wave
Type of Service . The (insert end product name) is
soldered.
All CH1786A products are hermetically
designed to be used on standard device telephone
sealed and will not be harmed by industry standard
lines. It connects to the telephone line by means of a
wave soldering processes.
standard jack called the USOC RJ-11C (or USOC
RJ45S). Connection to telephone-company-provided
Socketing.
The socketing approach to mounting
coin service (central office implemented systems) is
eliminates cleaning and desoldering concerns. When
prohibited. Connection to party lines service is subject
the socket is used, it must make a solid connection to
to state tariffs.
all pins.
Failure to do so will cause unreliable or
intermittent operation. Also, steps should be taken to
Changes in Attestation Procedure for Plugs and
assure that the module remains tightly seated in the
Jacks. (Name of applicant) attests that the network
socket during shipping. Cermetek recommends using
interface plugs or jacks used on this equipment comply
sockets from Samtec. See Application Note # 130,
with and will continue to comply with the mechanical
Summary of Recommended Suppliers.
requirements specified in Part 68, sub-part F,
specifically the dimensions, tolerances and metallic
plating requirements.
The compliance of these
connectors will be assured by purchase specifications
and incoming inspection.
Documentation of such
specifications and/ or inspections will be provided to
the FCC within 30 days of their request for the same.
Telephone Company Procedures. The goal of the
telephone company is to provide you with the best
service it can. In order to do this, it may occasionally
be necessary for them to make changes in their
equipment, operations or procedures.
If theses
changes might affect your service or the operation of
your equipment, the telephone company will give you
notice, in writing, to allow you to make any changes
necessary to maintain uninterrupted service.
Figure 5.
Speaker Control Circuit: Optional to
In certain circumstances, it may be necessary for the
allow for call progress monitoring.
telephone company to request information from you
concerning the equipment which you have connected
to your telephone line. Upon request of the telephone
FCC REGISTRATION
company, provide the FCC registration number and
All products in the CH1786A family are registered with
the ringer equivalence number (REN); both of these
the FCC (Federal Communications Commission)
items are listed on the equipment label. The sum of all
under Part 68.
To maintain the validity of the
of the REN’s on your telephone lines should be less
registration, you must serve notice to the end user of
than five in order to assure proper service from the
the products of several restrictions the FCC places on
telephone company. In some cases, a sum of five
the modem and its use.
may not be useable on given line.
Consult your
telephone provider.
In addition to restriction notification, the FCC requires
that Cermetek make all repairs to all products in the
If Problems Arise .
If any of your telephone
CH1786A family.
If repairs are necessary after
equipment is not operating properly, you should
installation of the CH1786A in the end product and the
immediately remove it from your telephone line, as it
end product has been delivered to the end user, the
may cause harm to the telephone network.
If the
end product must be returned to the end product
telephone company notes a problem, they may
supplier where the CH1786A can be removed and
temporarily discontinue service. When practical, they
then forward to Cermetek for repair. The following
will notify you in advance of this disconnection.
If
2006 Cermetek Microelectronics, Inc.
Page 14
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
advance notice is not feasible, you will be notified as
Minimum DTR pulse width =0.1 seconds
soon as possible.
Ring count =01
Escape code character =43
When you are notified, you will be given the
Carriage return character =13
opportunity to correct the problem and informed of
Line feed character =10
your right to file a complaint with the FCC. Contact
Back space character =08
your local telephone service provider if you have nay
Duration of wait for dial tone =02 seconds
questions about your phone line.
Duration of wait for carrier after dialing =30 seconds
Duration of dial pulse (comma)=02 seconds
In the event repairs are ever needed on the (insert
Carrier detect response time =0.1 seconds
your product name), they should be performed by
Escape code guard time =1 second
(insert your company name) or an authorized
Length of use after comma =2.0 seconds
representative of (insert your company name).
For
Last carrier to hang up delay =0.1 seconds
information contact: (insert your company address).
DTMF interdigit delay =0.1 seconds
Sleep mode inactivity time = off
Long space disconnect disabled
DEFAULT STATUS, PERFORMANCE, AND
V.22B selected
SPECIFICATIONS
Factory Defaults. The following is a summary of the
Factory Pre-Configuration. Cermetek pre-configures
Default Configuration Profile installed by Cermetek
the CH1786A modems with the following command
Microelectronics, Incorporated, prior to delivery of the
set:
CH1786A.
Enter: AT+MS=V22B,1,300,2400,300,2400<CR>
Async mode selected
Result: OK
2400bps
Even parity
Enter:
Auto answer enabled
ATS0=1%C0&C1&D0&S1&Q6\N0&Y0&W0<CR>
Command echo ON
Result: OK
Error correction OFF
All result codes enabled –extended
Wait for dial tone before dialing =2 seconds
IMPORTANT NOTE
Detects busy signal
Full word result codes
If the AT&F, AT&F0 or AT&F1 commands are
Pulse dial make/break ratio =39/61
executed by the user, the Factory Pre-configuration
DSR enabled
commands specified above must be executed after
Modem enabled DTR
the AT&F, AT&F0 or AT&F1 commands to ensure
DCD enabled
proper configuration setup of the CH1786A
Speaker enabled but off when receiving carrier
Speaker volume set to low
Guard tones disabled
2006 Cermetek Microelectronics, Inc.
Page 15
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
All models except
CH1786AL and CH1786AN
Figure 6.
PSTN Line Interface for all CH1786A Products. CH1786AL and CH1786AN models do NOT
contain internal Surge Protection (Dashed Box 2). The purchaser MUST be provide external
surge protection to maintain conveyed FCC Part 68 approval.
1. Current Limiting PSTN Protection Line Device.
For severe environments, use an external three
Current limiting devices are mandatory to meet UL
terminal device with an earth ground as is shown in
safety standards. To maintain conveyed FCC Part
dashed Box 3.
68 approval, the current limiting components
identified as F1 and F2 in dashed Box 1 must also
4. EMI/RFI Suppression.
survive FCC Part 68 surge testing.
Refer to
Suppression of emitted EMI/RFI is recommended
Cermetek Application Note #126, Supplemental
and is typically required to obtain FCC part 15 A
PSTN Line Protection, for more details. Refer to
and/or B approval. EMI/RFI suppression circuitry is
Application Note # 130, Summary of Recommend
also used to suppress reception of externally
Suppliers, for a list of suppliers and associated part
generated EMI/RFI signals, such as strong radio
numbers.
signals, should the CH1786A be located near a
source of such signals.
Although no external
A resettable/repairable fuse (rated at 0.15 amps) is
EMI/RFI noise suppression circuitry is required to
preferred because it resets automatically upon
maintain
conveyed
FCC
Part
68
approval,
removal of the current flow. Non-resettable devices
additional suppression may be added as described
are also acceptable.
Although CS-03 Part 1
below without adversely affecting FCC Part 68
(Canada) follows the requirements of FCC Part 68
approval.
(USA),
Cermetek
recommends
contacting
a
certified independent lab to verify compliance in the
specific application.
A. To provide adequate EMI/RFI suppression, the
capacitor/inductor network contained in dashed
2. Over Voltage and Lightning Protection.
Box 5 should be located as close to the RJ-11C
Surge Protection is provided by internal circuitry
Jack as possible. Further, this network should
contained within all CH1786A models except
be provided with an excellent ground path to the
CH1786AL and CH1786AN. No additional external
chassis.
components are required to maintain conveyed
FCC Part 68 approval for all models EXCEPT
B. Capacitors C1 and C2 should not exceed
CH1786AL and CH1786AN.
0.005 µ f. They must have a rating of 1.5KV and
typically are 0.001 µ f ± 20%. Inductors L1 and
For CH1786AL and CH1786AN, the required surge
L2 may be either individual inductors or a dual
protection (identified as D1 in Dashed Box 2) must
inductor. Refer to Application Note #130 for a
be supplied externally. The purchaser must include
list of suppliers. For UL applications, choose
some form of surge protection as described herein
capacitors and inductors that are UL 1950
to maintain conveyed FCC Part 68 approval. Refer
Edition 3 listed.
The actual values of the
to Application Note # 130 for a list of suppliers.
components used may vary depending on the
end product design and the nature of the EMI/
3. Optional External Over Voltage and Lightning
RFI.
Consult an FCC Part 15 consultant, if
Protection.
required.
In most environments, the internal two terminal
surge suppressor (see dashed Box 3) is adequate.
2006 Cermetek Microelectronics, Inc.
Page 16
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 7. CH1786A System Data Mode Compatibility Specifications.
Parameter
Specification
Parameter
Specification
Asynchronous
2400, 1200 600 bps character
Receive Carrier
Originate 2400Hz ± 7Hz
asynchronous.
Frequencies
Answer
1200Hz ± 7Hz
0-300 bps asynchronous
V.22 bis, V.22,
212A
Asynchronous
Speed
TXD may differ +1%, -2.5%
Bell 103
Answer
‘space’ 2020Hz ±
Range
from modem output. Offsets
7Hz
will be corrected by adding/
Answer
‘mark’
2225Hz ±
deleting stop bits.
7Hz
Originate ’space’
1070Hz ±
7Hz
Originate ‘mark’
1270Hz ±
7Hz
Asynchronous Format
8,9,10 bits, including start,
Receiver
OFF to ON threshold –43
stop, parity.
Sensitivity
dBm
ON to OFF threshold –48
dBm
Telephone Line Interface
Two-wire
full
duplex
over
Billing Delay
2.0 to 3.0 seconds (T a =25°C)
public switched network. On-
chip hybrid and billing delay
timers.
Modulation
V.22 bis, 16 point QAM at 600
Hysteresis
2 dB minimum
baud. V.22 and 212A, 4 point
DPSK at 600 baud.
103
Binary phase coherent FSK.
Self
Test
Pattern
Alternate ‘ones’ and ‘zeros’
Line
Fixed
compromise
Generator
and error detector, to be used
Equalization
equalization,
transmit.
along with most loopbacks. A
Adaptive
equalizer
for
number
indicating
the
bit
PSK/QAM, receive.
errors detected is sent to DTE.
Transmit
Carrier
Originate 1200Hz ± .01%
Diagnostic
Local analog loopback. &T1
Frequencies
V.22
bis,
Answer
2400Hz ± .01%
Available
Local analog loopback.
V.22, 212A
Must be used with error
correction off (AT&Q6).
Bell 103
Originate ’space’
1070Hz ±
Call Progress
With speaker or quiet screen
.01%
Tones Detected
messages (No dial tone,
Originate ‘mark’
1270Hz ±
busy, ring, modem answer
.01%
tone and voice).
Answer
‘space’ 2025Hz ±
Computer
IBX PC/XT/AT bus
.01%
Interface
compatible with an
Answer
‘mark’
2225Hz ±
8250/16450/16550A UART
.01%
as a serial controller.
2006 Cermetek Microelectronics, Inc.
Page 17
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 8. CH1786A Electrical Specifications.
Parameter
Description
Min.
Typ.
Max.
Units
V CC
Positive Supply Voltage- Noise less than 50mV
4.75
5.0
5.25
V
I CC Off Hook
Nominal Operating Current when modem is OFF Hook
61
67
mA
I CC On Hook
Nominal Operating Current when modem is ON Hook
58
64
mA
I CCPD
Power Down Current @
0.0
mA
2
V CC = 5.5V when modem is in Power Down Mode
I RIPD
Current Supplied into RI pin when in Power Down
11.0
uA
2
Mode @ V CC = 5.5V
1
V IH
High Level Input Voltage
2
Vcc+.
V
5
1
V IL
Low Level Input Voltage
0
0.8
V
I IN
Input Leakage Current (TXD, DTR, RTS)
-10
+10
uA
I LO
Leakage Current DCD, HS, RXD, SLEEP, DSR
-10
+10
uA
VT+
Positive Hysteresis Threshold for RESET pin
3.0
V
VT-
Negative Hysteresis Threshold for RESET pin
1.33
V
1
V OH
High Level Output Voltage (I OH = 2.0mA)
2.4
V
1
V OL
Low Level (I OL = - 2.0mA)
0.4
V
Test conditions: VCC = 5V ± 10%, Temp = 0 ° C to 70 ° F (unless otherwise stated).
Notes:
1. Output Load = 50 pF ± one TTL.
2. With recommended 30k ohm external resistor. Maximum external resistor range: 10k to 100k ohm.
Table 9. CH1786A Electrical Specifications.
Parameter
Minimum
Typical
Maximum
Units
Comments
DC Off Hook Impedance
125
312
Ohms
@16 to 80 ma
Trans Hybrid Loss
25
dB
600 Ohm, RXA, TXA
Ring Voltage Detect
25VAC
35VAC
V RMS
Typically riding on 48VDC
Line Loop Current-
16
80
mA
(Off-Hook)
Return Loss @ 1000Hz
15
dB
600 Ohm
Ring Detect Frequencies
14
20
35
Hz
Receiver Insertion Gain
-0.5
0.0
+0.5
dBm
600 Ohm- Data Mode
Transmit Power
-17.2
-13.0
-9.5
dBm
Into 600 Ohm Load
(Adjustable with S91)
First Character After Reset
0.5
1.0
5
sec
Delay
Inter Character Delay
20
50
msec
Between all command
characters
Command Delay
100
200
msec
Between all AT commands
Maximum Reset Drive
0
10K
Ohms
Minimum Reset Pulse
10
msec
If user supplied
Duration
2006 Cermetek Microelectronics, Inc.
Page 18
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 10. Other Performance Specifications.
Parameter
Minimum
Typical
Maximum
Units
Comments
DTMF total power
-5.3
-5.6
--5.8
dBm
Into 600 ohm load
DTMF Twist (Balance)
2
3
dB
DTMF Tone Duration
50
85
255
ms
85ms default
Pulse Dialing Rate
8
10
20
pps
10pps default
Pulse Dialing Make/
39/61
%
US, Canada default
Break
Pulse Interdigit Interval
700
3000
ms
789ms default
Guard Tone Frequency
1800
Hz
Referenced to High Channel
Transmit
Guard Tone Amplitude
-9
dB
Referenced to High Channel
Transmit
High Channel Transmit
-1
dB
Referenced to Low channel,
Amplitude
Guard tone enabled
nd
Guard Tone 2
-40
dB
Harmonic Distortion
Call Progress
205
720
Hz
@ -20 dBm received tone
Passband Frequency
Wait Time for Dial tone
2
255
sec
Two second default
Return loss @ 1000Hz
15
dB
T r =600 Ω
Table 11. Analog Characteristics.
Name
Type
Characteristic
Value
SPK
O(DF)
Minimum Load
300 Ω
Maximum Capacitive Load
0.01µ
Output voltage
1.65± .6V
2006 Cermetek Microelectronics, Inc.
Page 19
Document No. 607-0019 Revision A8 (03/06)
Cermetek Microelectronics, Inc.
CH1786A Family of Ultra Small 2400bps Modems
Table 12. CH1786A Pin Functions.
PACKAGE CONNECTION TABLE
PIN NO.
FUNCTION
PIN NO.
FUNCTION
1
RING
12
V/D
2
TIP
13
DTR
3
RXA
14
DSR
4
TXA
15
RI
5
SPK
16
CTS
6
NC
17
DCD
7
NC
18
NC
8
SLEEP
19
VCC
9
NC
20
GND
10
TXD
21
RST
11
RXD