CH1786 Family of Ultra Small 2400bps Modems
INTRODUCTION
FEATURES
The CH1786 family of modems are a full function,
  • Supports
  • Standards
    ITU-U
    V.22bis,V.22,Bell
    FCC Part 68 approved 2400bps modem.
    These
    212,and Bell 103
    modems provide a fast, easy and flexible way to
  • FCC Part 68 approved and DOT CSA CS-03 Part I
  • integrate a modem into any OEM product while
    approvable
    utilizing the minimum amount of PCB space (1.01 ”x
    1.27 ”x 0.52 ”). The CH1786 family only requires two
  • UL 1950 and CSA C22.2 950 Listed
  • external interfaces: a ITU-U V.24 serial interface that
  • UL File Number: E104957
  • can be routed directly to a UART, and a Tip and Ring
  • AT Command structure with extensions
  • interface which goes directly to an RJ-11 jack for the
    PSTN line connection.
    The CH1786 can be
  • 1500 VAC RMS isolation barrier minimum, 2122V
  • controlled with industry standard AT commands and,
    peak surge protection minimum
    hence,
    is
    compatible
    with
    available
    industry
  • Single 5 volt operation
  • communication software.
  • Low power operation with automatic reduced power
  • standby mode
    All CH1786 modems support asynchronous operation
    at 2400bps, 1200bps, and 300bps to both Bell and
  • Automatic
  • adaptive
    and
    fixed
    compromise
    ITU-U standards. The resident PSTN line interface,
    equalization
    or Data Access Arrangement (DAA), while being FCC
  • Size: 1.01 ”x 1.27 ”x 0.52 ”(nominal)
  • approved, is also Canadian DOT approvable and can
  • NVRAM allows storage of custom configurations
  • be approved in other countries that require 1500VAC
    and telephone numbers
    RMS isolation requirements per UL 1950 Edition 3.
    The CH1786 family of modems operate off a single 5-
    volt supply. The low power operation and automatic
    CH1786 FAMILY
    standby mode make these modems ideally suited for
    CH1786
    NVRAM, Voice/ Inject, Hermetic,
    portable equipment. In addition, their small physical
    Operating Temperature:
    size affords maximum flexibility in equipment design.
    0 ° C to +70 ° C
    CH1786ET
    NVRAM, Voice/
    Inject, Hermetic,
    Operating Temperature:
    -40 ° C to +85 ° C
    CH1786NH
    Non-Hermetic, Operating
    Temperature:
    0 ° C to +70 ° C
    Figure 1. Functional Block Diagram of CH1786.
    The CH1786 comes with FCC Part 68 approval and is
    shipped from the factory with an FCC Part 68 label
    indicating
    the
    registration
    number
    and
    ringer
    equivalent.
    This label should be prominently
    displayed on the end product.
    Figure 2. Voice/ Data Port Control
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    CH1786 Family of Ultra Small 2400bps Modems
    DESCRIPTION OF FUNCTIONAL BLOCKS
    AT Command Set. A 40-character command line is
    AND DISCUSSION OF BASIC OPERATIONS
    supported. The command line starts with AT and
    Figure 1 contains a functional block drawing of the
    may contain standard or enhanced commands. The
    CH1786. The CH1786 is a highly integrated, full-
    commands are compatible with EIA Document
    function
    modem,
    comprised
    of
    a
    modulator/
    TR302.2/88-08006.
    demodulator, controller, NVRAM and an FCC Part 68
    approved and UL 1950/CSA C22.2 950 listed PSTN
    Serial Host Interface. The serial interface is a V.24
    line interface.
    (EIA-232) compatible interface. Ten Bits total: 1 start
    bit, 1 stop bit, and eight data bits which can be either
    Modulation/Demodulation and Modem Controller.
    eight bits with no parity or seven odd or even with
    These functions are provided by a monolithic modem
    parity. The start bit is LOW going. RXD and TXD
    integrated circuit.
    This IC has built-in facilities to
    data is non-inverted. See pin description in Table 2.
    accommodate integrated AT command control and
    contains the necessary resident interfaces for general
    Speaker Interface.
    The SPK output reflects the
    communication and routing to the DAA.
    receiver analog input and provides a signal that can
    be used to monitor call progress. The SPK signal can
    Telephone Line Interface or DAA. The CH1786
    drive a 300 load directly. Typically, the SPK signal
    family of modems is designed to meet 1500VAC RMS
    is input into an audio power amplifier and the
    isolation and provide 2122V peak surge protection.
    amplifier, in turn, drives the speaker coil.
    The
    Consequently, the CH1786 satisfies U.S. FCC Part
    speaker is activated with the ATMn command. The
    68
    and
    DOT
    CSA
    CS-03
    Part
    I
    Canadian
    speaker volume is adjusted using the ATLn
    requirements, and will meet other international
    command, where n is 0, 1, 2, or 3.
    Increasing
    approval agency requirements that specify these
    numbers correspond to higher volume.
    Figure 6
    levels of isolation.
    indicates one method of driving an external 8
    speaker.
    With the exception of the U.S., most countries
    (including Canada) require submission of the final
    Phone Control. Cermetek’s CH1786 contains a pin
    product or system containing the CH1786 to the
    called Voice or Data (V/D). The V/D pin toggles high
    appropriate governing regulatory agency for approval.
    when the modem goes off hook. This pin can be
    Typically this is accomplished by submitting the final
    used to activate a relay which can switch a telephone
    end product to an independent test house or
    on or off the Tip and Ring incoming PSTN lines. This
    consultant for evaluation.
    The test house or
    feature allows any telephone associated with the
    consultant then forwards the test results and
    CH1786 to be disconnected when a data call is in
    applicable documents to the regulatory agency. Call
    progress, thereby preventing the data from being
    Cermetek for a list of suggested consultants.
    disturbed by an inadvertent telephone pick-up. See
    Figure 2.
    Non-Volatile RAM (NVRAM). The NVRAM present
    on the CH1786 is sufficient to store up to two user
    Speed and Parity Selection. Prior to call initiation,
    customized modem configurations.
    The AT&Wn
    the host controller trains the modem to the host
    command will store the active modem configuration in
    speed (2400,1200 or 300bps) and parity (odd, even,
    the selected NVRAM locations by specifying an n of 0
    mark, space, or none) via a host-initiated training
    or 1.
    sequence. This training also sets the speed of the
    data
    for
    originate
    calls.
    The
    CH1786
    will
    The
    AT&Yn
    command
    selects
    the
    modem
    automatically adjust to the originator’s speed when
    configurations to be automatically recalled and made
    answering calls.
    active upon a reset or power up.
    The ATZn
    command immediately recalls and activates a stored
    The CH1786 matches the host’s parity when it returns
    configuration. Refer to Tables 4, 5 and 6 for storable
    status messages to the host.
    During a data
    S-Registers and available commands.
    connection, however, the modem passes parity
    through without interpretation or alteration.
    The NVRAM can save up to four telephone numbers
    with up to 36 digits or modifiers in each telephone
    Sleep Mode. To minimize power consumption, the
    number. The AT&Zn=s command will store s, the
    CH1786 includes a power down feature called Sleep
    telephone number dial string. The individual NVRAM
    Mode.
    When
    activated,
    the
    CH1786
    will
    telephone number storage locations are selected by
    automatically enter Sleep Mode after 0 to 254
    specifying an n of 0, 1, 2, or 3.
    The ATDTS=n
    seconds of inactivity. The inactivity delay is selected
    command will cause the modem to dial the stored
    using the ATS24 command.
    The CH1786 is
    telephone number in location n. NVRAM is not
    delivered from the factory with a 5 second inactivity
    available on the CH1786LC or CH1786NH.
    delay enabled (i.e., ATS24=5 ). The CH1786 returns
    SUPPORT FEATURES
    to normal operation when a ring signal is received or
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    CH1786 Family of Ultra Small 2400bps Modems
    upon an input low signal on the TXD pin.
    pin becomes active. The CH1786ET products can
    ATS24=255 disables the Sleep Mode and is the
    thus be powered down to zero.
    default if no value is set in register S24.
    Table 1. Connection Rates.
    A SLEEP output signal is available to control power to
    Answering
    Connection Rate Resulting
    external devices. In Figure 6, a FET controlled by the
    Modem Initial
    When Calling Modem Initial
    SLEEP signal turns of the external speaker amplifier
    Trained Rate
    Rate Is:
    when the CH1786 enters Sleep Mode.
    In Sleep
    300
    1200
    2400
    Mode, power is reduced to approximately 50% of
    300
    300
    1200
    1200
    normal operating power.
    1200
    300
    1200
    1200
    2400
    300
    1200
    2400
    Guard Tone. A guard tone of 550 Hz or 1800 Hz can
    be generated at 6 dB or 9 dB below the transmit level,
    respectively, by using the &Gn command. Refer to
    “Cermetek AT Commands and S-Registers reference
    Guide”
    or
    the
    Cermetek
    web
    site
    at
    http://www.cermetek.com.
    Answer Tone. A ITU-U (2100 Hz) or Bell (2225Hz)
    answer tone is generated depending on the selected
    configuration. Refer to “Cermetek AT commands and
    S-Registers Reference Guide” or the Cermetek web
    site at http://www.cermetek.com.
    Data Encoding. The data encoding conforms to ITU-
    U recommendations V.22bis or V.22, or Bell212A, or
    103, depending on the selected configuration. Refer
    to
    “Cermetek
    AT
    commands
    and
    S-Register
    Reference Guide” or the Cermetek web site at
    http://www.cermetek.com.
    Line Equalization. Transmitter and receiver digital
    filters compensate for delay and amplitude distortion
    Figure 3. Zero Power Operation.
    during operation on nominal phone lines. In addition,
    automatic adaptive equalization in the receiver
    Referring to Figure 3, the controller activates the relay
    minimizes the effects of inter symbol interference.
    switch, supplying power (+5V) to the CH1786ET. In
    this configuration, the ring signal is used to “wake up”
    Transmission Speed.
    In normal operation, the
    the CH1786ET when the CH1786ET is in the power
    originating modem initiates the call and attempts to
    down state.
    connect to the answering modem at a speed
    The pins of the CH1786ET will be in an undefined
    established by the originating modem’s controller
    state when power is switched off. This must be taken
    prior to call initiation. This is referred to as the Initial
    into consideration to assure that no unwanted signals
    Trained Rate. Upon receiving the call, the answering
    are presented to the CH1786ET during power down.
    modem will attempt to connect to the originating
    modem at its Initial Trained Rate. If these two rates
    Ring Indicator (RI). The RI pin follows the frequency
    are identical, the connection is made. If the speeds
    of the ring signal and toggles low when the CH1786
    differ, the answering modem must adjust its rate or
    detects an incoming call. The ring signal is typically
    terminate the call. Table 1 indicates the connection
    20 to 30 Hz and is on for 2 seconds and off for 4
    rate that will result when the calling modem’s Initial
    seconds. Although not TTL compliant, the RI pin can,
    Trained Rate and the answering modem’s Initial
    nonetheless, be utilized to activate external circuitry
    Trained Rate are different.
    including the external RST pin.
    NOTE
    When using the RI pin, it is recommended that a
    A 2400-baud connection rate will only result if both
    Schmitt Trigger or the Isolated Envelope Detect
    modems are initially set at 2400 baud.
    Circuit in Figures 3 or 5 be placed between the RI pin
    and the external load.
    Zero Power Mode (CH1786ET only).
    If an
    application calls for zero power during standby
    Power Supply. The CH1786 modem module is a
    periods, the power may be switched off using external
    complex set of sub-systems. During the course of
    circuitry and then reapplied when the CH1786’s RI
    normal operation the CH1786 decodes analog signals
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    CH1786 Family of Ultra Small 2400bps Modems
    from the telephone line that are in the millivolt range.
    Enter: ATS7=255<CR>
    Disables data-carrier time
    Steps must be taken by the user to guarantee that
    Result: OK
    out
    power supply noise on all supply lines, including
    ground, does not exceed 50 mV peak to peak. Any
    Enter: ATS10=255<CR> Disables lost-carrier time
    frequency between 20 kHz and 150 kHz must be less
    Result: OK
    out
    than 500 micro volts peak.
    If necessary, use
    dedicated power and ground planes.
    Failure to
    The following command sequences illustrate
    provide such operating conditions could cause the
    implementation of common Voice/Tone Port
    CH1786 to malfunction or to function erratically.
    applications.
    The CH1786 requires a single +5V ±5% supply. It is
    1. To answer a voice call.
    recommended that by-pass capacitors be placed on
    (a) Enter: ATH1<CR>
    the power supply as close to the modem’s supply
    Result: OK
    input as practical.
    It’s recommended a 10 µ F
    Tantalum capacitor in parallel with a 0.01 µF ceramic
    (b) Drive V.INJ. HIGH to activate relay.
    capacitor be used.
    (c) Begin voice conversation.
    Voice/DTMF Tone Injection Port.
    The CH1786
    2. To switch to data mode.
    provides two pins to allow the user to share the
    (a) Drive V.INJ. LOW
    telephone line interface associated with the modem
    (b) At the originate modem:
    for voice and DTMF applications. Figure 4 contains a
    Enter: ATX1<CR>
    schematic indicating one possible configuration for
    Result: OK
    voice/ tone utilization.
    3. To disconnect (hang-up) a voice call or a data
    WARNING
    call.
    The CH1786 has been FCC Part 68 approved as a
    (a) Enter: ATH<CR>
    data modem only. Utilization of the Voice/DTMF
    Result: OK
    Tone Port requires further registration. FCC will
    require that the system, including the CH1786 and
    4. To place a call to 1234567 using the CH1786’s
    the handset or DTMF transceiver, adhere to Part 68
    DTMF tone generator.
    rules.
    Voice/Tone Injection is not active on
    (a) Enter: ATDT1234567;C0<CR>
    CH1786NH.
    Result: OK
    (b) Drive V.INJ. HIGH
    Typically, voice communication would precede data
    communications.
    For this case, the following
    commands should be used to configure the CH1786
    MODEM CONTROL
    (Refer to Figure 4):
    The CH1786 modem may be controlled by sending
    serial ASCII command sequences. The commands
    are sent to the modem serially on the TXD pin. After
    execution of a received command, the modem
    returns a serial status message that can be read on
    pin RXD.
    This message indicates command
    completion status. Refer to Table 3 for a complete
    list of status messages.
    INITIALIZING THE MODEM
    Before commands may be sent to the CH1786, the
    CH1786 must be initialized. Initialization is a two step
    activity consisting of:
    1. Hard Reset. This is accomplished by applying a
    hardware reset pulse to pin RST or by switching
    the power off and then back on.
    2. Initial modem training.
    The CH1786 must be
    Figure 4. Voice/Tone Injection.
    trained to the host’s speed (2400, 1200, 300bps)
    and parity (odd, even, mark, space or none).
    Enter: ATS0=<CR>
    Disables auto-answer
    Result: OK
    These activities are briefly described below.
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    CH1786 Family of Ultra Small 2400bps Modems
    Reset. Upon applying power to the CH1786, the
    <CR> represents carriage return (ASCII 13
    CH1786 automatically generates an internal reset
    or HEX 0D).
    pulse. The user may also reset the modem externally
    by applying a high-going reset pulse to the RST pin
    When entering commands to the modem, the
    for at least 10ms after the +5V power supply has
    backspace character-control-H (ASCII 8 or HEX 08)
    stabilized. Delay sending commands to CH1786 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
    CH1786 time to properly reconfigure.
    command line. A command line may be as long as
    40 characters, excluding the letters AT . By way of
    Training the Modem. Each modem must be trained
    example, the command below instructs the CH1786
    to match its host’s speed and parity so that it is able
    to configure itself to not echo characters when in
    to recognize serial asynchronous commands sent to it
    command mode E0 and then put itself in answer
    by the host’s is UART. The host must retrain the
    mode A .
    modem each time a reset pulse is applied on RST or
    after a RESET serial command has been issued.
    Enter: ATE0A<CR>
    Result: OK
    Modem Training Command Sequence.
    The
    CH1786 is trained by sending it the following
    AT Command Set. The available command set is
    sequence:
    divided into four types of commands: dial modifiers,
    basic
    commands,
    ampersand
    and
    percent
    Enter: AT<CR>
    commands. Refer to the complete list in Table 5.
    Result: OK
    Where: A and T may be either upper or lower case
    AT Command Data Rate. With the serial interface,
    but must be the same case.
    the rate is speed sensed for parity and format.
    <CR> represents carriage return
    The AT sequence is referred to as an attention
    THE STATUS MESSAGES
    sequence. The CH1786 will respond with one of the
    The CH1786 responds with a status message after
    following status messages, depending on whether it
    each command is executed. This status message
    is optioned for Terse (abbreviated) or Verbose
    may either be a single digit followed by a carriage
    (English) status messages.
    return or a carriage return and line feed with a
    message in English, followed by a carriage return and
    Result: 0<CR> (Terse)
    line feed.
    or
    The basic status code subsets are enabled with the
    Result:
    <CR><LF>OK<CR><LF> (Verbose)
    Xn command.
    Where n=0,1,2,3,4 establishes the
    Where:
    <CR> represents carriage return (ASCII 13
    result codes allowed by the user.
    or HEX 0D).
    <LF> represents line feed (ASCII 10 or
    X0:
    Result Codes 0, 1, 2, 3, 4 allowed
    HEX 0A).
    X1:
    Result Codes 0, 1, 2, 3, 4, 5, 10 allowed
    X2:
    Result Codes 0,1, 2, 3, 4, 5, 6, 10 allowed
    After responding with an OK, the CH1786 is in idle
    X3:
    Result Codes 0, 1, 2, 3, 4, 5, 7, 10 allowed
    mode and is ready to accept additional commands.
    X4:
    Result Codes 0, 1, 2, 3, 4, 5, 6, 7, 10 allowed.
    An alternate attention sequence A/ may be sent
    which behaves much like the AT sequence except
    NOTE
    that it causes the previously entered command
    The CH1786 is factory set to X4, which allows all
    specified with an AT prefix to be executed. When
    result codes.
    given, both the AT and A/ must be in upper case
    ASCII.
    No carriage return is needed for the A/
    command.
    MODEM STATES
    The CH1786 can be in either command mode or data
    THE COMMAND FORMAT
    mode. When the modem is idle, it is in command
    Typical commands consist of three elements: the
    mode by default and will recognize commands.
    attention sequence, the commands themselves, and
    When data transmission is in progress, the CH1786 is
    a terminating carriage return.
    in the data mode state and will not recognize
    commands.
    To force the CH1786 to recognize
    AT[commands]<CR>.
    commands, the host must send an escape sequence
    Where: AT represents attention sequence.
    to the CH1786 forcing it out of data mode and into
    [Commands] represents command strings.
    command mode.
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    CH1786 Family of Ultra Small 2400bps Modems
    Figure 5. CH1786 Application Diagram
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    CH1786 Family of Ultra Small 2400bps Modems
    Table 2. CH1786 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. Not active in
    CH1786NH.
    4
    TXA
    I
    ANALOG VOICE INJECTED . Transmit Signal. Let float if not used. Not active in
    CH1786NH.
    5
    SPK
    O
    SPEAKER . Audio output for speaker. See speaker control schematic in Figure 6.
    6
    NC
    -
    No connection.
    7
    NC
    -
    No connection.
    8
    SLEEP
    O
    SLEEP . A LOW indicates CH1786 is in low power idle mode. Used to control
    power to other devices. See Figure 6. Register S24 is the sleep timer register.
    When the CH1786 is inactive for a period of time specified by S24, the CH1786 will
    power down by about 50% of its normal operating power. During power down, all
    I/O lines become undefined. The CH1786 products are shipped from the factory
    with a 5 second inactivity timer (ATS24=5) enabled.
    9
    NC
    -
    No connection.
    10
    TXD
    I
    TRANSMIT DATA . Serial Transmit data input. Marking or a binary 1 condition is
    transmitted when a HIGH is asserted.
    11
    RXD
    O
    RECEIVE DATA .
    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 CH1786 is off-
    hook and online. Therefore, this pin also reflects the state of the off-hook relay of
    the CH1786. See Figure 2.
    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 .
    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.
    16
    CTS
    O
    CLEAR-TO SEND . Ground if not using the FAX option. Reserved for flow control
    when using FAX option. CTS only active on CH1786 when S24=255.
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    CH1786 Family of Ultra Small 2400bps Modems
    Table 2. CH1786 Pin Descriptions Continuation
    PIN
    NAME
    TYPE
    FUNCTION
    17
    DCD
    O
    DATA CARRIER DETECT . LOW indicates a data carrier from a remote modem is
    detected. Must be enabled using the &C1 command.
    18
    HS
    O
    SPEED INDICATION . HIGH speed select output. A low on this pin indicates the
    modem is operating at 2400bps.
    19
    VCC
    -
    POWER SUPPLY . 5 volts + 5% Note: Noise should be less than 50mV peak to
    peak.
    20
    GND
    -
    GROUND . Note: Noise should be less than 50mV peak to peak.
    RST
    1
    21
    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 to enable internal reset.
    22
    NC
    -
    No connection required. For CH179X or CH2056 compatibility, connect to GND or
    use as an active LOW input for request to send ( RTS ) functionality for CH179X/2056
    products.
    Note:
    (1) If VCC has a slow power up ramp time, the internal reset may be ineffective.
    (2) Do not drive LED’s directly from any output. Use Buffers.
    Table 3. Summary of Result Codes and Meanings.
    Result Codes
    Status Message
    Meaning
    0
    OK
    Command Executed
    1
    CONNECT
    Carrier detected at 300bps
    2
    RING
    Ring Detected
    3
    NO CARRIER
    Did not detect carrier
    4
    ERROR
    Entry error
    5
    CONNECT 1200
    Carrier detected at 1200bps
    6
    NO DIAL TONE
    Off-hook, but no response after 5 seconds
    7
    BUSY
    Busy signal detected
    10
    CONNECT 2400
    Carrier detected at 2400bps
    The escape sequence consists of a “guard time” (a
    The CH1786 will stay off-hook with its carrier on after
    period where no characters are sent to the modem),
    the escape sequence is received. It will return an OK
    followed by 3 escape characters, followed by another
    status message when it is ready to accept
    guard time. The guard time is set by register S12.
    commands. The CH1786 may be put into data mode
    The escape character code is set in register S2. At
    by issuing the command ATO<CR> .
    power-up, the guard time is set to 1 second minimum,
    and the escape character is set as “+.” There is no
    minimum delay between characters but the maximum
    delay is set by register S12.
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    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    AT COMMAND APPLICATIONS
    Example: Use A/ , the repeat command, to redial the
    Dialing A Phone Number. The Dial command takes
    last telephone number dialed.
    the form Dn , where n is a string of characters. In the
    Enter:
    A/
    simplest form, n will be only the digits of the phone
    Result:
    ATDT1234567R<CR> Previous command
    number to be dialed.
    OK
    line executed
    Example: Tone Dial number.
    Return to Command State.
    Use ; to return to
    Enter:
    ATD1234567<CR>
    command mode offer dialing.
    Result:
    OK
    Example: Touch-tone dial 9, pause, dial number,
    In response to this command, the CH1786 dials the
    return to Command.
    telephone number “123-4567” and then waits for a
    Enter:
    ATDT9,1234567;<CR>
    carrier from the distant modem.
    If no carrier is
    Result:
    OK
    detected within a given time (the default time is 30
    seconds), the CH1786 automatically releases the line
    Automatic Answering. The SO register controls the
    and sends a NO CARRIER result code. If a carrier is
    number of rings that must occur before the modem
    detected, the CH1786 gives a CONNECT result code
    answers a call. The register may range in value from
    and goes on-line, permitting communication with the
    0 to 255.
    distant modem.
    S0 =
    0 DO NOT ANSWER TELEPHONE
    S0 =
    1 ANSWER ON RING 1
    The Dial Command may also be issued without a
    S0 =
    2 ANSWER ON RING 2
    telephone number. ATD causes the modem to pick
    S0 =
    3 ANSWER ON RING 3
    up the telephone line without dialing a number.
    S0 =
    255 ANSWER ON RING 255
    Pause During Dialing. When placing a call from an
    When S0 is set to 0, the modem will not auto-answer.
    office with a telephone connected to a PBX, it may be
    necessary to dial an access code (usually the digit 9)
    The Serial Interface Lines. The CH1786 supports a
    to get an outside line.
    Inserting a comma in the
    full EIA-232D/V.24 serial interface. Signal levels are
    telephone number instructs the modem to pause for a
    TTL rather than EIA-232D level compatible, which
    specific length of time. The factory set default pause
    allows direct connection of the CH1786 to the host
    time is 2 seconds.
    UART without the need for level translation circuitry.
    See Table 2 for a complete pin description.
    Example: Pulse Dial 9,pause, dial number.
    Enter:
    ATDP9,1234567<CR>
    The CH1786 is controlled by sending it serial
    Result:
    OK
    commands over TXD and its status determined by
    monitoring the serial status messages returned on
    Multiple commas may be used to generate integer
    RXD. DTR is optionally used to reset, terminate calls
    multiples of the specified delay time.
    or return CH1786 to command mode.
    Originate a Call in Answer Mode. The D command
    All other serial interface lines may be utilized for the
    forces the modem into originate mode. To call an
    convenience of a particular application but are not
    originate-only modem, dial the number and set the
    required by the CH1786.
    Unused outputs (from
    modem to answer mode via the R command (reverse
    modem) should be left unconnected. Unused inputs
    originate). This is done by including an R at the end
    should be set to the proper logic level. See Table 2.
    of the telephone number.
    Fax Modes. The CH1786 Product Family supports
    Example: Change modem
    from original-only
    to
    Send and Receive FAX. The modes and rates are
    answer mode.
    determined by the AT+F commands. Refer to Table
    Enter:
    ATDT1234567R<CR>
    6A.
    Result:
    OK
    FAX modem processing is explicitly defined in ITU-U
    Multiple commas may be used to generate integer
    V.29, ITU-U V.27, and ITU-U V.21 recommendations.
    multiples of the specified delay time.
    All modulation, wave-form spectrum, and data
    processing functions conform to the appropriate
    Redial Last Number.
    The repeat command is a
    specifications.
    convenient way to execute the previously entered
    command line.
    2004 Cermetek Microelectronics, Inc.
    Page 9
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 4.
    S-Register Summary.
    Firmware
    Factory
    Register
    Description
    Range
    Units
    Saved
    Defaults
    Defaults
    S0
    Ring to Answer On
    0-255
    rings
    *
    000
    001
    S1
    Ring Count
    0-255
    rings
    000
    000
    S2
    Escape Code Character
    0-127
    ASCII
    043
    043
    S3
    Carriage Return Character
    0-127
    ASCII
    013
    013
    S4
    Line Feed Character
    0-127
    ASCII
    010
    010
    S5
    Back Space Character
    0-32, 127
    ASCII
    008
    008
    S6
    Maximum Wait Time for Dial Tone
    2-255
    s
    002
    002
    S7
    Maximum Wait Time for Data Carrier
    1-255
    s
    030
    030
    S8
    Pause Time for Comma
    0-255
    s
    002
    002
    S9
    Carrier Detect Response Time
    1-255
    1/10s
    006
    006
    S10
    Lost Carrier to Hang-up Delay
    1-255
    1/10s
    014
    014
    S11
    DTMF Dialing Speed
    50-255
    ms
    095
    095
    S12
    Escape Code Guard Time
    0-255
    1/50s
    050
    050
    S13
    Reserved
    -
    -
    -
    000
    000
    S14
    Bit Mapped Options Register
    Bit Mapped
    none
    *
    170 (AAH)
    170 (AAH)
    S15
    Reserved
    -
    -
    -
    000
    000
    S16
    Modem Test Options
    Bit Mapped
    none
    000
    000
    S17
    FAX Mode Null Byte Timer
    0-255
    4ms incr
    000
    000
    S18
    Test Timer
    0-255
    s
    *
    000
    000
    S19
    Protocol Interface Speed
    0-1
    none
    000
    000
    S20
    FAX Mode Inactivity Timer
    0-127
    s
    000
    000
    S21
    Bit Mapped Option Register
    Bit Mapped
    none
    *
    000
    096 (06H)
    S22
    Bit Mapped Option Register
    Bit Mapped
    none
    *
    118 (76H)
    118 (76H)
    S23
    Bit Mapped Option Register
    Bit Mapped
    none
    *
    007 (07H)
    023 (17H)
    S24
    Sleep Mode Inactivity Timer
    0-255
    s
    000
    000
    S25
    Delay to DTR Off
    0-255
    0.1 or 1s
    *
    005
    005
    S26
    RTS to CTS Delay Interval
    0-255
    0.01s
    *
    001
    001
    S27
    Bit Mapped Option Register
    Bit Mapped
    none
    *
    064 (40H)
    064 (40H)
    S28
    Bit Mapped Option Register
    Bit Mapped
    none
    *
    000
    001
    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.
    NOTE
    The CH1786LC and CH1786NH products do not contain NVRAM and, therefore, do not support data storage after
    power down. A detailed definition of all commands and S-Registers is available from Cermetek Microelectronics,
    Inc. Refer to Cermetek Document AT Commands and S-Registers Reference Guide or access our website at
    www.cermetek.com.
    2004 Cermetek Microelectronics, Inc.
    Page 10
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 5. CH1786 AT Command Set Summary.
    Table 6C. Ampersand and Percent Commands.
    Basic
    Function
    Ampersand
    Commands
    Commands
    Function
    AT
    Attention Code
    &Cn*
    Data Carrier Detect Option
    A
    Answer command
    &Dn*
    Data Terminal Ready Option
    A/
    Repeat last Command
    &Fn
    Restore Active Profile
    Bn*
    Communications Standard Option
    &Gn*
    Guard Tone Option
    D
    Dial Command
    &Pn*
    Make to Break Ratio Section
    E*
    Off-Line Character Echo Option
    &Sn*
    Data Set Ready Option
    Hn
    Switch Hook Control Option
    &Tn
    Test Command Option
    Ln*
    Speaker Volume Option
    &V
    View Active Configuration
    Mn*
    Speaker Control Option
    &Wn*
    Store Active Profile
    On
    On-Line Command
    &Yn*
    Set Profile to be used after hard
    Qn*
    Result Code Display Option
    reset
    Sn
    Select an S Register
    &Zn*
    Store Telephone Numbers
    Sn=
    Write to an S Register
    Sn?
    Read an S Register
    Vn*
    Result code Form Option
    PHONE LINE CONNECTION GUIDELINES
    Xn*
    Result Code Set/Call Progress
    1. The CH1786 must be mounted in the final
    Option
    assembly such that it is isolated from exposure to
    +++
    Escape Sequence
    any hazardous voltages within the assembly.
    ,
    Pause
    Adequate separation and restraint of cables and
    ?
    Returns Last addressed S-Register
    cords must be provided.
    Yn*
    Long Space Disconnect Option
    Fn
    On Line Echo character Option
    2. The circuitry from the CH1786 to the telephone
    Zn
    Restore Active Profile
    line interface must be provided in wiring that
    carries no other circuitry other than that
    specifically allowed in the FCC rules (such as A
    Table 6A. FAX Command Set Summary.
    and A1 leads).
    FAX Command
    Function
    +FCLASS=n
    Select Service Class
    3. Connection to phone line should be made
    +F<command>?
    Report Active Configuration
    through an RJ-11C jack.
    +F<command>=?
    Report Operating Capabilities
    +FAA=n
    Data/Fax Auto Answer
    4. PCB traces from the modem’s RING and TIP pins
    +FF
    Enhanced Flow Control
    to the RJ-11C jack must be 0.1 inch spacing or
    +FTS=n
    Stop Transmission and Wait
    greater to one another and 0.2 inch spacing or
    +FTM=n
    Transmit Data
    greater to all other traces.
    The traces should
    +FTH=n
    Receive Data
    have a nominal width of 0.020 inches or greater.
    +FTH=n
    Transmit Data with HDLC
    Framing
    5. The RING and TIP PCB traces should be as
    +FRH=n
    Receive Data with HDLC
    short as possible and oriented to prevent
    Framing
    coupling other high speed or high frequency
    +FRT=n
    Receive Test Data
    signals present on the host circuit PCB.
    +FTTn=m
    Transmit test Data
    6. No additional circuitry other than that shown in
    Table 6B. Dial Modifiers Summary.
    Figure 7A or 7B may be connected between the
    modem module and the RJ-11C jack. Doing so
    Dial Modifiers
    Function
    will invalidate the FCC approval.
    P
    Pulse Dial
    R
    Originate Call in Answer Mode
    7. The CH1786LC, and CH1786NH (only) requires
    T
    Touch Tone Dial
    external surge protection (see Figure 7B). This is
    W
    Wait for Dial Tone
    mandatory to maintain FCC Part 68 conveyed
    ;
    Return to Idle State
    approval.
    @
    Wait for Quiet Answer
    Command
    8. The CH1786, the RJ-11C jack, the interfacing
    !
    Flash Hook
    circuitry and all PCB traces in between, must be
    ,
    Pause
    contained on a PCB with a 94 V-0 flammability
    0-9
    Allowed Dial Digits/Characters
    rating.
    A,B,C,D, #, *
    2004 Cermetek Microelectronics, Inc.
    Page 11
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    9. The supplied FCC registration label must be
    FCC REGISTRATION
    applied visibly on the outside of the product.
    All products in the CH1786 family are registered with
    the FCC
    (Federal Communications Commission)
    10. The product’s User Manual must provide the user
    under Part 68.
    To maintain the validity of the
    with instructions for connection and use as
    registration, you must serve notice to the end user of
    recommended in the FCC Registration Section
    the products of several restrictions the FCC places on
    below.
    the modem and its use.
    In addition to restriction notification, the FCC requires
    CH1786 HANDLING AND ASSEMBLY
    that Cermetek make all repairs to all products in the
    RECOMMENDATIONS
    CH1786 family.
    If repairs are necessary after
    The CH1786 contains static-sensitive components
    installation of the CH1786 in the end product and the
    and should only be handled by personnel and in
    end product has been delivered to the end user, the
    areas that are properly protected against static
    end product must be returned to the end product
    discharge.
    The
    two
    recommended
    mounting
    supplier where the CH1786 can be removed and then
    techniques for physically connecting the CH1786 to a
    forward to Cermetek for repair. The following notice
    PCB are discussed below.
    is recommended and should be included in the end
    product’s user manual.
    FOR YOUR USER’S MANUAL
    The FCC Part 68 rules require the following (or
    equivalent) be provided to the end user of equipment
    containing a DAA.
    Type of Service . The (insert end product name) is
    designed to be used on standard device telephone
    lines. It connects tot he telephone line by means of a
    standard jack called the USOC RJ-11C (or USOC
    RJ45S). Connection to telephone-company-provided
    coin service (central office implemented systems) is
    prohibited.
    Connection to party lines service is
    subject to state tariffs.
    Changes in Attestation Procedure for Plugs and
    Figure 6.
    Speaker Control Circuit: Optional to
    Jacks. (Name of applicant) attests that the network
    allow for call progress monitoring.
    interface plugs or jacks used on this equipment
    comply with and will continue to comply with the
    Direct Soldering.
    The CH1786 may be wave
    mechanical requirements specified in Part 58, sub-
    soldered.
    All CH1786 products are hermetically
    part F, specifically the dimensions, tolerances and
    sealed (except the CH1786NH) and will not be
    metallic plating requirements.
    The compliance of
    harmed
    by
    industry
    standard
    wave
    soldering
    these connectors will be assured by purchase
    processes. Cermetek recommends against exposing
    specifications
    and
    incoming
    inspection.
    the non-hermetic CH1786NH to aqueous based
    Documentation of such specifications and/ or
    rinsing processes.
    inspections will be provided to the FCC within 30
    days of their request for the same.
    Socketing.
    The socketing approach to mounting
    eliminates cleaning and desoldering concerns. When
    Telephone Company Procedures. The goal of the
    the socket is used, it must make a solid connection to
    telephone company is to provide you with the best
    all pins.
    Failure to do so will cause unreliable or
    service it can. In order to do this, it may occasionally
    intermittent operation. Also, steps should be taken to
    be necessary for them to make changes in their
    assure that the module remains tightly seated in the
    equipment, operations or procedures.
    If theses
    socket during shipping. Cermetek recommends using
    changes might affect your service or the operation of
    sockets from Samtec. See Application Note # 130,
    your equipment, the telephone company will give you
    Summary of Recommended Suppliers.
    notice, in writing, to allow you to make any changes
    necessary to maintain uninterrupted service.
    2004 Cermetek Microelectronics, Inc.
    Page 12
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    In certain circumstances, it may be necessary for the
    DEFAULT STATUS, PERFORMANCE, AND
    telephone company to request information from you
    SPECIFICATIONS
    concerning the equipment which you have connected
    to your telephone line.
    Upon request of the
    The following is a summary of the Default
    telephone company, provide the FCC registration
    Configuration Profile installed by Cermetek
    number and the ringer equivalence number (REN);
    Microelectronics, Incorporated, prior to delivery
    both of these items are listed on the equipment label.
    of the CH1786.
    The sum of all of the REN’s on your telephone lines
    should be less than five in order to assure proper
    Async mode selected
    service from the telephone company. In some cases,
    2400bps
    a sum of five may not be useable on given line.
    Bell 212A operation at 1200bps
    Consult your telephone provider.
    Even parity
    Auto answer enabled (Disabled on CH1786NH)
    If Problems Arise .
    If any of your telephone
    Command echo ON
    equipment is not operating properly, you should
    All result codes enabled –extended
    immediately remove it from your telephone line, as it
    Wait for dial tone before dialing =2 seconds
    may cause harm to the telephone network. If the
    Detects busy signal
    telephone company notes a problem, they may
    Full word result codes
    temporarily discontinue service. When practical, they
    Pulse dial make/break ratio =39/61
    will notify you in advance of this disconnection. If
    DSR enabled
    advance notice is not feasible, you will be notified as
    Modem ignores DTR
    soon as possible.
    DCD enabled (Disabled on CH1786NH)
    When you are notified, you will be given the
    Speaker enabled but off when receiving carrier
    opportunity to correct the problem and informed of
    Speaker volume set to medium
    your right to file a complaint with the FCC. Contact
    Local modem will grant RDL request from remote
    your local telephone service provider if you have nay
    modem
    questions about your phone line.
    Guard tones disabled
    Minimum DTR pulse width =0.1 seconds
    In the event repairs are ever needed on the (insert
    Ring count =01 (CH1786)
    your product name), they should be performed by
    Escape code character =43
    (insert your company name) or an authorized
    Carriage return character =13
    representative of (insert your company name). For
    Line feed character =10
    information contact: (insert your company address).
    Back space character =08
    Duration of wait for dial tone =02 seconds
    Duration of wait for carrier after dialing =30 seconds
    Duration of dial pulse (comma)=02 seconds
    Carrier detect response time =0.1 seconds
    Escape code guard time =1 second
    Length of use after comma =2.0 seconds
    Last carrier to hang up delay =0.1 seconds
    DTMF interdigit delay =0.1 seconds
    DTMF Attenuation =-4dB
    Sleep mode inactivity time =5 seconds
    Long space disconnect disabled
    2004 Cermetek Microelectronics, Inc.
    Page 13
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Figure 7.
    PSTN Line Interface for all CH1786 Products.
    1. Currently Limiting PSTN Protection Line
    protection as indicated in dashed Box 4 MUST BE
    Device.
    included when using CH1786NH products.
    Currently limiting devices are mandatory to meet
    UL safety standards. To maintain conveyed FCC
    4. Optional External Over Voltage and Lightning
    Part 68 approval, the current limiting components
    Protection.
    identified as F1 and F2 in dashed Box #1 must
    In most environments, the internal two terminal
    also survive FCC Part 68 surge testing. Refer to
    surge suppressor (see dashed Box 3) is adequate.
    Cermetek Application Note #126, Supplemental
    For severe environments, use an external three
    PSTN Line Protection, for more details. Refer to
    terminal device with an earth ground as is shown
    Application Note # 130, Summary of Recommend
    in dashed Box 4.
    Suppliers, for a list of suppliers and associated
    part numbers.
    5. EMI/RFI Suppression.
    EMI/RFI suppression is recommended. This is for
    A resettable/repairable fuse (rated at 0.15 amps)
    obtaining FCC part 15 A and/or B. It is also used
    is preferred because it resets automatically upon
    to suppress external EMI / RFI signals that can
    removal of the current flow.
    Non-resettable
    affect modem operation, such as strong radio
    devices are also acceptable. Although CSA CS-
    signals, should the modem be near a source of
    03 Part 1 (Canada) follows the requirements of
    such signals.
    No external EMI/RFI noise
    FCC Part 68 (USA), Cermetek recommends
    suppression circuitry is required to maintain
    contacting DOT (Canada) and/or a certified
    conveyed FCC Part 68 approval.
    Additional
    independent lab to verify compliance.
    suppression may be added as described below
    without adversely affecting FCC Part 68 approval.
    2. PSTN Current Limiting Resistors.
    Low value (10 Ω ) carbon film 1/4 watt resistors may
    A. To provide adequate EMI/RFI suppression,
    be required (identified as R1 and R2 in dashed
    the capacitor/inductor network contained in
    Box 2), depending on end product application
    dashed Box 5 should be located as close to
    environment, to enhance performance by reducing
    the RJ-11C Jack as possible.
    Further, this
    susceptibility to PSTN current surges that may
    network should be provided with an excellent
    occur before the OVERVOLTAGE PROTECTION
    ground path to the chassis.
    device (identified as D1 in dashed Box 3)
    B. Capacitors C1 and C2 should not exceed
    becomes fully activated.
    0.005 µ f. They must have a rating of 1.5KV
    and typically are 0.001 µ f ± 20%. Inductors L1
    Refer to Cermetek Application Note # 130,
    and L2 may be either individual inductors or a
    Summary of Recommended Supplies, for a list of
    dual inductor. Refer to Application Note #130
    suppliers.
    for a complete list of recommended vendors
    and associated part numbers.
    For UL
    3. Over Voltage and Lightning Protection.
    applications, choose capacitors and inductors
    Surge Protection is provided by internal circuitry
    that are UL 1950 listed. The actual values of
    contained within all CH1786s (except CH1786NH).
    the components used may vary depending on
    No additional external components are required to
    the end product design and the nature of the
    maintain conveyed FCC Part 68 approval for all
    EMI/ RFI. Consult an FCC part 15 consultant
    CH1786s Products (except CH1786NH). External
    if required.
    2004 Cermetek Microelectronics, Inc.
    Page 14
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 7. CH1786 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 dBm
    stop, parity.
    Sensitivity
    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.
    Frequencies V.22 bis,
    Answer
    2400Hz ± .01%
    Available
    Local analog loopback.
    V.22, 212A
    Remote digital loopback.
    Request
    remote
    digital
    loopback.
    Local
    interface
    loopback
    modem with self-test.
    Bell 103
    Originate ’space’
    1070Hz ±
    Call Progress
    With speaker or quiet screen
    .01%
    Tones Detected
    messages (No dial tone, busy,
    Originate ‘mark’
    1270Hz ±
    ring-back, modem answer tone
    .01%
    and voice).
    Answer
    ‘space’ 2020Hz ±
    Computer
    IBX PC/XT/AT bus compatible
    .01%
    Interface
    with an 8250/16450/16550A
    Answer
    ‘mark’
    2225Hz ±
    UART as a serial controller.
    .01%
    2004 Cermetek Microelectronics, Inc.
    Page 15
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 8. CH1786 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
    50
    75
    mA
    I CC On Hook
    Nominal Operating Current when modem is ON Hook
    25
    50
    mA
    I CCPD
    Power Down Current
    10
    mA
    V IH
    High Level Input Voltage*
    2
    V
    V IL
    Low Level Input Voltage*
    -0.3
    0.8
    V
    I IN
    Input Leakage Current (TXD, DTR, RTS)
    15
    100
    uA
    I LO
    Leakage Current DCD, HS, RXD, SLEEP, DSR
    10
    uA
    C P
    Capacitive Lead (TXT, DTR, RST)
    10
    pF
    VT+
    Positive Hysteresis Threshold for RESET pin
    2.5
    V
    VT-
    Negative Hysteresis Threshold for RESET pin
    1.8
    V
    V OH
    High Level (I OH = 0.5mA)*
    2.4
    V
    V OL
    Low Level (I OL = 1.6mA)*
    0.6
    V
    Test conditions: VCC = 5V ± 10%, Temp = 0 ° C to 70 ° F (unless otherwise stated).
    *Output Load = 50 pF ± one TTL.
    Table 9. CH1786 Electrical Specifications.
    Parameter
    Minimum
    Typical
    Maximum
    Units
    Comments
    Off Hook Impedance
    20
    Ohms
    Trans Hybrid Loss
    25
    dB
    600 Ohm, RXA, TXA
    Ring Voltage Loop
    75V
    250V
    V pp
    On 48VDC line voltage for
    sustained periods
    Line Loop Current-(Off-
    20
    100
    mA
    Hook)
    Return Loss @ 1000Hz
    15
    dB
    600 Ohm
    Ring Frequencies
    40
    Hz
    Receiver Insertion Gain
    -0.5
    0.0
    +0.5
    dBm
    600 Ohm- Data Mode
    Transmit Power
    -9.5
    dB
    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
    Minimum Reset Pulse
    10
    msec
    If user supplied
    Duration
    2004 Cermetek Microelectronics, Inc.
    Page 16
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 10. Other Performance Specifications.
    Parameter
    Minimum
    Typical
    Maximum
    Units
    Comments
    Tone 2 Harmonic
    nd
    -35
    dB
    HYB enabled into 600 Ω
    Distortion
    DTMF Twist (Balance)
    3
    dB
    DTMF Tone Duration
    50
    255
    ms
    95ms default
    Pulse Dialing Rate
    8
    10
    20
    pps
    10pps default
    Pulse Dialing Make/
    39/61
    %
    US, Canada default
    Break
    Pulse Dialing Make/
    33/67
    %
    UK, Hong Kong
    Break
    Pulse Interdigit
    700
    3000
    ms
    789ms default
    Interval
    Guard Tone
    550
    Hz
    Referenced to High Channel
    Frequency
    Transmit
    Guard Tone Amplitude
    -6
    dB
    Referenced to High Channel
    Transmit
    Guard Tone
    1800
    Hz
    Referenced to High Channel
    Frequency
    Transmit
    Guard Tone Amplitude
    -9
    dB
    Referenced to High Channel
    Transmit
    High Channel
    -1
    dB
    Referenced to Low channel,
    Transmit Amplitude
    Guard tone enabled
    nd
    Guard Tone 2
    -40
    dB
    Harmonic Distortion
    Call Progress
    120
    620
    Hz
    Passband Frequency
    Wait Time for Dial tone
    2
    255
    sec
    Two second default
    Return loss @ 1000Hz
    30
    dB
    T r =600 Ω + 2.16 µF
    Table 11. Analog Characteristics.
    Name
    Type
    Characteristic
    Value
    SPK
    O(DF)
    Minimum Load
    300 Ω
    Maximum Capacitive
    0.01µ
    Load
    10 Ω
    Output Impedance
    2.5± 1.6V
    Output voltage
    <20mV
    D.C. Offset
    2004 Cermetek Microelectronics, Inc.
    Page 17
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 12. CH1786 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
    HS
    8
    SLEEP
    19
    VCC
    9
    NC
    20
    GND
    10
    TXD
    21
    RST
    11
    RXD
    22
    NC
    Figure 8.
    CH1786 Physical Dimensions.
    2004 Cermetek Microelectronics, Inc.
    Page 18
    Document No. 607-0004 Revision L4 (08/04)
    Cermetek Microelectronics, Inc.
    CH1786 Family of Ultra Small 2400bps Modems
    Table 13. Summary CH1786 Family of Products.
    Operating
    Model
    Summary of Features
    Temperature
    CH1786
    Full function, Voice/Inject, NVRAM, FCC Part 68 approved, UL 1950
    0°C to 70°C
    Listed, Hermetic
    CH1786ET
    Full function, Voice/Inject, NVRAM, Zero Power Option, FCC Part 68
    -40°C to 85°C
    Approved, UL 1950 Listed, Hermetic
    CH1786FX
    Full function, FAX, Voice/Inject, NVRAM, FCC Part 68 approved, UL
    0°C to 70°C
    1950 Listed, Hermetic
    CH1786LC
    Full function, Voice/Inject, FCC Part 68 Approved, UL 1950 Listed,
    0°C to 70°C
    Hermetic
    CH1786NH
    Full function, FCC Part 68 Approved, Non-Hermetic, Listed UL 1950
    0°C to 70°C
    Cermetek reserves the right to make changes in specifications at any time and without notice. The information furnished by
    Cermetek in this publication is believed to be accurate and reliable. However, Cermetek assumes no responsibility for its use, or for
    any infringements of patents or other rights of third parties resulting from its use. No license is granted under any patents or patent
    rights of Cermetek.
    Cermetek provides the user with a FCC/DOT Approved or Approvable device. However Cermetek does not have influence or
    knowledge of Application environment.
    Therefore, for FCC Approved or Approvable devices, the user assumes all risk for
    maintaining compliance to registration.
    Printed in U.S.A
    406 TASMAN DRIVE | SUNNYVALE CA 94089 | LOCAL: 408-752-5000 | TOLL FREE: 1-800-882-6271 | FAX: 408-752-5004
    CERMETEK WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
    iModem Network WEB SITE: http://www.imodem.net/ or https://sunnyvale.imodem.net/
    2004 Cermetek Microelectronics, Inc.
    Page 19
    Document No. 607-0004 Revision L4 (08/04)