ETC CH1786LC

CH1786 Family of Ultra Small
2400 bps Modems
INTRODUCTION
Figure 1. Functional Block Diagram of CH1786.
The CH1786 family of modems offer the smallest footprint
commercially available for a full function, FCC Part 68 approved
2400bps modem. These modems provide a fast, easy and flexible
way to integrate a modem into any OEM product while utilizing
the minimum amount of PCB space (1.0 ”x 1.25 ”x 0.53 ”). The
CH1786 family only requires two external interfaces: a CCITT
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 CH1786 can be controlled with
industry standard AT commands and, hence, is compatible with
available industry communication software.
All CH1786 modems support asynchronous operation at
2400bps, 1200bps, and 300bps to both Bell and CCITT
standards. The resident PSTN line interface, or Data Access
Arrangement (DAA), while being FCC approved, is also Canadian
DOT approveable and can be approved in other countries that
require 1500VAC RMS isolation requirements per UL 1950.
The CH1786 family of modems operate off a single 5-volt supply.
The low power operation and automatic standby mode make
these modems ideally suited for portable equipment. In addition,
their small physical size affords maximum flexibility in equipment
design.
FEATURES
• Supports Standards CCITT V.22bis,V.22,Bell 212,and Bell 103
• FCC Part 68 approved and DOT CSA CS-03 Part I approveable
• UL 1950 and CSA C22.2 950 Listed
• AT Command structure with extensions
• 1500 VAC RMS isolation barrier minimum, 2122V peak surge
protection minimum
• Single 5 volt operation
• Low power operation with automatic reduced power standby
mode
• Automatic adaptive and fixed compromise equalization
• Test modes and diagnostics
• Size:1.0 ”x 1.25 ”x 0.53 ”(nominal)
• NVRAM allows storage of custom configurations and telephone
numbers
CH1786 Family Includes:
CH1786LC
Operating
CH1786NH
CH1786
CH1786ET
CH1786FX
2400bps Modem, voice/ Inject, Hermetic
DESCRIPTION OF FUNCTIONAL BLOCKS AND
DISCUSSION OF BASIC OPERATIONS
Figure 1 contains a functional block drawing of the CH1786. The
CH1786 is a highly integrated, full-function modem, comprised of
a modulator/ demodulator, controller, NVRAM (Non-Volatile RAM)
and an FCC Part 68 approved PSTN line interface DAA (Data
Access Arrangement).
Modulation/Demodulation and Modem Controller.
These functions are provided by a monolithic modem integrated
circuit. This IC has built-in facilities to accommodate integrated
AT command control and contains the necessary resident
interfaces for general communication and routing to the DAA.
Telephone Line Interface or DAA.
The CH1786 family of modems is designed to meet 1500VAC
RMS isolation and provide 2122V peak surge protection.
Consequently, the CH1786 satisfies U.S. FCC Part 68 and DOT
CSA CS-03 Part I Canadian requirements, and will meet other
international approval agency requirements that specify these
levels of isolation.
Figure 2. Voice/ Data Port Control
Temperature: 0°C to +70°C
2400bps Modem, No Voice/Inject, Non-hermetic
Operating Temperature: 0°C to +70°C
2400bps Modem, NVRAM, Voice/ Inject,
Operating Temperature: 0°C to +70°C
2400bps Modem, NVRAM, Voice/
Inject, Hermetic, Operating Temperature:
–40°C to +85°C
Same as CH1786 with send and receive
fax capability
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.
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
With the exception of the U.S., most countries (including
Canada) require submission of the final product or system
containing the CH1786 to the appropriate governing
regulatory agency for approval. Typically this is accomplished
by submitting the final end product to an independent test
house or consultant for evaluation. The test house or
consultant then forwards the test results and applicable
documents to the regulatory agency. Call Cermetek for a list
of suggested consultants.
Non-Volatile RAM (NVRAM).
The NVRAM present on the CH1786 is sufficient to store up
to two user customized modem configurations. The AT&Wn
command will store the active modem configuration in the
selected NVRAM locations by specifying an n of 0 or 1.
The AT&Yn command selects the modem configurations to
be automatically recalled and made active upon a reset or
power up. The ATZn command immediately recalls and
activates a stored configuration. Refer to Tables 4, 5 and 6
for storable S-Registers and available commands.
The NVRAM can save up to four telephone numbers with up
to 36 digits or modifiers in each telephone number. The
AT&Zn=s command will store s, the telephone number dial
string. The individual NVRAM telephone number storage
locations are selected by specifying an n of 0,1,2,or 3. The
ATDTS=n command will cause the modem to dial the stored
telephone number in location n. NVRAM is not available on
the CH1786LC or CH1786NH.
SUPPORT FEATURES
“AT ”Command Set.
A 40-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.
See pin description in Table 2.
Speaker Interface.
The SPK output reflects the receiver analog input and
provides a signal that can be used to monitor call progress.
The SPK signal can drive a 300 Ω load directly. Typically, the
SPK signal is input into an audio power amplifier and the
amplifier, inturn, drives the speaker coil. The speaker is
activated with the ATMn command. The speaker volume is
adjusted using the ATLn command, where n is 0,1,2,or 3.
Increasing numbers correspond to higher volume. Figure 6
indicates one method of driving an external 8 Ω speaker.
Phone Control.
Cermetek s’ CH1786 contains a pin called Voice or Data
(V/D). The V/D pin toggles high when the modem goes off
hook. This pin can be used to activate a relay which can
switch a telephone on or off the Tip and Ring incoming PSTN
lines. This feature allows any telephone associated with the
CH1786 to be disconnected when a data call is in progress,
thereby preventing the data from being disturbed by an
inadvertent telephone pick-up. See Figure 2.
Sleep Mode.
To minimize power consumption, the CH1786 includes a power down
feature called Sleep Mode. When activated, the CH1786 will
automatically enter Sleep Mode after 0 to 254 seconds of inactivity.
The inactivity delay is selected using the ATS24 command. The
CH1786 is delivered from the factory with a 5 second inactivity delay
enabled (i.e., ATS24=5). The CH1786 returns to normal operation
when a ring signal is received or upon an input low signal on the TXD
pin. ATS24 = 255 disables the Sleep Mode and is the default if no
value is set in register S24.
A SLEEP output signal is available to control power to external
devices. In Figure 6, a FET controlled by the SLEEP signal turns of
the external speaker amplifier when the CH1786 enters Sleep Mode.
In Sleep Mode, power is reduced to approximately 50% of normal
operating power.
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 command &Gn.
Refer to “Cermetek AT Commands and S-Registers reference Guide”
or the Cermetek web site at http://www.cermetek.com
Answer Tone.
A CCITT (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 CCITT recommendations V.22 bis 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 during operation on nominal phone lines. In
addition, automatic adaptive equalization in the receiver minimizes the
effects of intersymbol 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 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 that will result when the calling
modem’s Initial Trained Rate and the answering modem’s Initial
Trained Rate are different.
Note that a 2400 baud connection rate will only result if both modems
are initially set at 2400 baud.
Table 1. Connection Rates.
Speed and Parity Selection.
Prior to call initiation, the host controller trains the modem to
the host speed (2400,1200,or 300 bps) and parity (odd, even,
mark, space, or none)via a host-initiated training sequence.
This training also sets the speed of the data for originate
calls. The CH1786 will automatically adjust to the originator ’s
speed when answering calls.
The CH1786 matches the host ’s parity when it returns status
messages to the host. During a data connection, however,
the modem passes parity through without interpretation or
alteration.
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
2
Zero Power Mode (CH1786ET only).
If an application calls for zero power during standby periods,
the power may be switched off using external circuitry and
then reapplied when the CH1786 ’s RI pin becomes active.
The CH1786ET products can thus be powered down to zero.
Figure 3. Zero Power Operation
When using the RI pin, it is recommended that a Schmitt Trigger or the
Isolated Envelope Detect Circuit in Figures 3 or 5 be placed between
the RI pin and the external load.
Power Supply.
The CH1786 modem module is a complex set of sub-systems. During
the course of normal operation the CH1786 decodes analog signals
from the telephone line that are in the millivolt range. Steps must be
taken by the user to guarantee that power supply noise on all supply
lines, including ground, does not exceed 50 mV peak to peak. Any
frequency between 20 kHz and 150 kHz must be less than 500 micro
volts peak. If necessary, use dedicated power and ground planes.
Failure to provide such operating conditions could cause the CH1786 to
malfunction or to function erratically.
The CH1786 requires a single +5V ±5%supply. It is recommended that
by-pass capacitors be placed on the power supply as close to the
modem’s supply input as practical. It’s recommended a 10 µF Tantalum
capacitor in parallel with a 0.01 µF ceramic capacitor be used.
Voice/ Tone Injection Port.
The CH1786 provides two pins to allow the user to share the telephone
line interface associated with the modem for voice and DTMF
applications. Figure 4 contains a schematic indicating one possible
configuration for voice/ tone utilization.
Referring to Figure 3, the controller activates the relay switch,
supplying power (+5V to the CH1786ET-UL.
In this
configuration, the ring signal is used to “wake up ”the
CH1786ET-UL when the CH1786ET-UL is in the power down
state.
WARNING: The CH1786 has been FCC Part 68 approved as a data
modem only. Utilization of the Voice/Tone Port requires further
registration. FCC will require that the system , including the
CH1786 and the handset or DTMF transceiver, adhere to Part 68
rules. Voice/Tone Injection is not active on CH1786NH.
Figure 4. Voice/ Tone Injection
The pins of the CH1786ET-UL will be in an undefined state
when power is switched off. This must be taken into
consideration to assure that no unwanted signals are
presented to the CH1786ET-UL during power down.
Ring Indicator (RI).
The RI pin follows the frequency of the ring signal and toggles
low when the CH1786 detects an incoming call. The ring
signal is typically 20 to 30 Hz and is on for 2 seconds and off
for 4 seconds. Although not TTL compliant, the RI pin can,
nonetheless, be utilized to activate external circuitry including
the external RST pin.
Typically, voice communication would precede data communications.
For this case, the following commands should be used to configure the
CH1786 (Refer to Figure 4):
Enter: ATS0=[CR]
Disables auto-answer
Enter: ATS7=255[CR]
Eliminates hang-up due to
Enter: ATS10=255[CR]
lack of carrier signal.
The following command sequences illustrate implementation of
common Voice/Tone Port applications.
1. To answer a voice call:
(a) Enter: ATH1[CR]
(b) Drive V.INJ. HIGH to activate relay.
(c) Begin voice conversation.
2000 Cermetek Microelectronics, Inc.
2.
To switch to data mode, drive V.INJ. LOW, then:
(a) At the originate modem:
Enter: ATX1[CR]
3.
To disconnect (hang-up) a voice call or a data call:
Enter: ATH[CR]
4.
To place a call using the CH1786’s DTMF:
(a) Enter ATDT#;C0[CR]
(b) Drive V.INJ high
Document No. 607-0004 ECN 8176 Rev. H (03/00)
3
Figure 5. CH1786 Application Diagram
Table 2. CH1786 Pin Descriptions
PIN
NAME
TYPE
1
RING
I/O
Directly connects to the telephone line’s Ring lead through a user supplied RJ-11C jack.
2
TIP
I/O
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.
2000 Cermetek Microelectronics, Inc.
FUNCTION
Document No. 607-0004 ECN 8176 Rev. H (03/00)
4
Table 2. CH1786 Pin Descriptions (Continued)
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 output. 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 output is 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. See Figure 2.
13
DTR
I
DATA TERMINAL READY input. Active LOW. Switching off DTR can either return modem to
command state, disconnect phone call, or reset modem. DET should be set LOW when not
used.
14
DSR
O
DATA SET READY output. 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. Output always LOW. Reserved for flow control when using FAX option.
Currently, CTS only active on CH1786FX when S24=255. No power down mode option
available. Effective 31 May 2000, CTS will be active on CH1786 also.
17
DCD
O
DATA CARRIER DETECT. LOW indicates a data carrier from a remote modem is detected.
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.
21
RST1
I
RESET input. 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.
Note: (1) If VCC has a slow power up ramp time, the internal reset may be ineffective.
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
5
MODEM CONTROL
AT [commands] [CR].
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.
Where: AT represents attention sequence.
[commands ] represents command strings.
[CR ] represents carriage return (ASCII 13 or HEX 0D).
INITIALIZING THE MODEM
Before commands may be sent to the CH1786,the modem
must be initialized. This consists of two events:
1) 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 modem must be trained to the
host ’s speed (2400,1200,300bps) and parity (odd, even, mark,
space or none).
When entering commands to the modem, the backspace character-control-H (ASCII 8 or HEX 08)can be used to edit mistakes.
“AT ”and “A/”may not be edited however. Multiple commands
may be placed in the 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 CH1786 to configure
itself to not echo characters when in command mode (E0)and
then put itself in answer mode (A).
Enter:ATE0A [CR ]
AT Command Set.
These activities are briefly described below.
The available command set is divided into four types of commands: dial modifiers, basic commands, ampersand and percent
commands. Refer to the complete list in Table 5.
Reset.
AT Command Data Rate.
Upon applying power to the CH1786, the CH1786 automatically generates an internal reset pulse. The user can also
reset the modem externally by applying a high-going reset
pulse to the RST pin for at least 10ms after the +5V power
supply has stabilized. Delay sending commands to CH1786
for 200ms after reset has been initiated to allow the CH1786
time to properly reconfigure.
With the serial interface, the rate is speed sensed for parity and
format.
Training the Modem.
Each modem must be trained to match its host ’s speed and
parity so that it is able to recognize serial asynchronous
commands sent to it by the host UART. The host must retrain
the modem each time a reset pulse is applied on RST or after
a RESET serial command has been issued.
Modem Training Command Sequence.
The CH1786 is trained by sending it the following sequence:
Enter: AT [CR ]
Where: A and T may be either upper or lower case but must
be the same case.
[CR ] represents carriage return
THE STATUS MESSAGES
The CH1786 responds with a status message after each command is executed. This status message may either be a single
digit followed by a carriage return or a carriage return and line
feed with a message in English, followed by a carriage return and
line feed.
The basic status code subsets are enabled with the Xn command. Where n=0,1,2,3,4 establishes the result codes allowed
by the user.
X0 -Result Codes 0, 1, 2, 3, 4 allowed
X1 -Result Codes 0, 1, 2, 3, 4, 5, 10 allowed
X2 -Result Codes 0,1, 2, 3, 4, 5, 6, 10 allowed
X3 -Result Codes 0, 1, 2, 3, 4, 5, 7, 10 allowed
X4 -Result Codes 0, 1, 2, 3, 4, 5, 6, 7, 10 allowed
The CH1786 is factory set to X4, which allows all result codes.
Table 3. Summary of Result Codes and Meanings.
The “AT” sequence is referred to as an attention
sequence. The CH1786 will respond with one of the
following status messages, depending on whether it is
optioned for abbreviated or English status messages.
Result: 0 [CR ]
(Abbreviated form)
Result: [CR ][LF ] OK [CR ][LF ] English form)
Where: [CR ] represents carriage return (ASCII 13 or HEX
0D).
[LF ] represents line feed (ASCII 10 or HEX 0A).
The modem is now in idle mode and is ready to accept commands. An alternate attention sequence “A/”may be sent
which behaves much like the AT sequence except that it
causes the previously entered command specified with an AT
prefix to be executed. When given, it must be in upper case
ASCII. No carriage return is needed.
THE COMMAND FORMAT
Typical commands consist of three elements: the attention
sequence, the commands themselves, and a terminating
carriage return.
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
6
Table 4. CH1786 Register Summary
Register
Function
Ring to Answer On
S0*
Ring Count
S1
Escape Code Character
S2
Carriage Return Character
S3
Line Feed Character
S4
Back Space Character
S5
Wait for Dial tone
S6
Wait for Data Carrier
S7
Pause Time for Comma
S8
Carrier Detect Response Time
S9
Lost Carrier to Hang-up Delay
S10
DTMF Dialing Speed
S11
Escape Code Guard Time
S12
Bit Mapped Options Register
S14*
Modem Test Options
S16
Test Timer
S18*
Bit Mapped Options Register
S21*
Bit Mapped Options Register
S22*
Bit Mapped Options Register
S23*
Sleep Mode Inactivity Time
S24
Delay to DTR
S25*
Bit Mapped Options Register
S27*
Bit Mapped Options Register
S28*
Table 5. CH1786 “AT” Command Set Summary
Basic Commands
Function
Attention Code
AT
Answer command
A
Repeat last Command
A/
Communications Standard Option
*BN
Dial Command
D
Off-Line Character Echo Option
*E
Switch Hook Control Option
Hn
Speaker Volume Option
*Ln
Speaker Control Option
*Mn
On-Line Command
On
Pulse Dial
P
Result Code Display Option
*Qn
Select an S Register
Sn
Write to an S Register
Sn=
Read an S Register
Sn?
Result code Form Option
*Vn
Result Code Set/Call Progress Option
*Xn
Escape Code Sequence Pause
+++
Pause
,
Returns Last addressed S Register
?
Long Space Disconnect Option
*Yn
On Line Echo character Option
Fn
Reset
Z
*=S-Registers stored in NVRAM upon receipt of &W command
Table 6. Fax Command Set Summary
Fax Command
Function
+FCLASS=n
+F<command>?
+F<command>=?
+FAA=n
+FF
+FTS=n
+FTSM=n
+FTH=n
+FTH=n
+FRH=n
+FRT=n
+FTTn=m
Select Service Class
Report Active Configuration
Report Operating Capabilities
Data/Fax Auto Answer
Enhanced Flow Control
Stop Transmission and Wait
Transmit Data
Receive Data
Transmit Data with HDLC Framing
Receive Data with HDLC Framing
Receive Test Data
Transmit test Data
Dial Modifiers
P
R
T
W
;
@
!
,
0-9
A,B,C,D
Function
Pulse Dial
Originate Call in Answer Mode
Touch Tone Dial
Wait for Dial Tone
Return to Idle State
Wait for Quiet Answer Command
Flash Hook
Paul
Dial Digits/Characters
Ampersand Commands
MODEM STATES
The CH1786 can be in either command mode or data mode.
When the modem is idle, it is in command mode by default and
will recognize commands. When data transmission is in
progress, the CH1786 is in the data mode state and will not
recognize commands. To force the CH1786 to recognize
commands, the host must send an “escape sequence ” to the
CH1786 forcing it out of data mode and into command mode.
The escape sequence consists of a “guard time” (a period
where no characters are sent to the modem), followed by 3
escape characters, followed by another guard time. At powerup, the guard time is set to 1 second minimum, and the escape
character is set as “+.” These two parameters can be modified
via registers S12 and S2, respectively.
The CH1786 will stay off-hook with its carrier on after the
escape sequence is received and it returns an OK status
message when it is ready to accept commands. The CH1786
can be put into data mode by issuing the command ATO [CR ].
2000 Cermetek Microelectronics, Inc.
*&Cn
*&Dn
&F
*&Gn
*&Pn
*&Sn
&Tn
&V
*&Wn
*&Yn
*&Zn
Function
Data Carrier Detect Option
Data Terminal Ready Option
Load Factory Defaults
Guard tone Option
Make to Break Ratio Selection
Data Set Ready Option
Test Command Option
View Active Configuration
Store active profile
Recall active profile
Store telephone numbers
Percent Commands
Function
%Dn
DTMF Attenuation
%J
Load Secondary Factory Defaults
*=Commands that can be stored in NVRAM. Not supported by the
CH1786LC or CH1786NH.
NOTE: A detailed definition of all commands and registers is
available from Cermetek Microelectronics, Inc. Refer to
Cermetek Document “AT Commands and S-Registers
Reference Guide” or access our web site at
www.cermetek.com.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
7
AT COMMAND APPLICATIONS
Dialing A Phone Number.
The Dial command takes the form Dn, where n is a string of characters. In the simplest form, n will be only the digits of the phone
number to be dialed.
Example: Dial number.
Enter: AT D1234567
In response to this command, the CH1786 dials the telephone
number “123-4567 ” and then waits for a carrier from the distant
modem. If no carrier is detected within a given time (the default
time is 30 seconds),the CH1786 automatically releases the line
and sends a NO CARRIER result code. If a carrier is detected,
the CH1786 gives a CONNECT result code and goes on-line,
permit-ting communication with the distant modem.
The Dial Command may also be issued without a telephone
number. ATD causes the modem to pick up the telephone line
without dialing a number.
Pause During Dialing.
When placing a call from an office with a telephone connected to
a PBX, it may be 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 specific length of
time. The factory set default pause time is 2 seconds.
Example: Dial 9,pause, dial number.
Enter: AT DT9,1234567
Multiple commas may be used to generate integer multiples of
the specified delay time.
Originate a Call in Answer Mode.
The D command forces the modem into originate mode. To call
an originate-only modem, dial the number and set the modem to
answer mode via the R command (reverse originate). This is
done by including an R at the end of the telephone number.
Example: Change modem from original-only to answer mode.
Enter: AT DT 1234567R
S0 =0 DO NOT ANSWER TELEPHONE
S0 =1 ANSWER ON RING 1
S0 =2 ANSWER ON RING 2
S0 =3 ANSWER ON RING 3
S0 =255 ANSWER ON RING 255
When S0 is set to 0,the modem will not auto-answer.
The Serial Interface Lines.
The CH1786 supports a full EIA-232D/V.24 serial interface.
Signal levels are TTL rather than EIA-232D level compatible, which allows direct connection of the CH1786 to
the host UART without level translating circuitry. See
Table 2 for a complete pin description.
The modem is controlled by sending it serial commands
over TXD and can be monitored by serial status messages
returned on RXD. DTR is optionally used to reset, terminate calls or return CH1786 to command mode.
All other serial interface lines may be utilized for the convenience of a particular application but are not required by
the CH1786. Unused outputs (from modem)should be left
unconnected. Unused inputs should be set to the proper
logic level. See Table 2.
FAX MODES (CH1786FX only)*
The CH1786FX supports Send and Receive Fax in addition
to the modem functions as defined by CH1786.
FAX modes and rates are determined by the AT+F
commands. Refer to Table 6.
FAX modem processing is explicitly defined in CCITTV.29,
CCITTV.27, and CCITT V.21 recommendations. All modulation, wave-form spectrum, and data processing functions conform to the appropriate specifications.
For additional information on CCITT recommendations,
contact Omnicom, Tel: 703-281-1135 or see CONEXANT’s
RC224ATF Designer ’s Guide, Tel: 714-221-4600.
Figure 6. Speaker Control Circuit— optional to
allow for call progress monitoring.
Redial Last Number.
Use A/, the repeat command, to redial the last telephone number
dialed.
Return to Command State.
Example: Touch-tone dial 9, pause, dial number, return for Command.
Example:
Enter:
Result:
Touch-tone dial 9, pause, dial number, return for
command.
AT DT9,1234567;
OK
Automatic Answering.
The S0 register controls the number of rings that must occur
before the modem answers a call. The register may range in
value from 0 to 255.
*Note: Currently the CH1786FX product performs the FAX function while the CH1786 does not. Special order version of the CH1786 are
available upon request that perform both data and FAX functions. Effective May 31, 2000 only the combined Data + FAX CH1786 will be
available.
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
8
PHONE LINE CONNECTION GUIDELINES
1) The CH1786 must be mounted in the final assembly such that
it is isolated from exposure to any hazardous voltages within the
assembly. Adequate separation and restraint of cables and cords
must be provided.
2) The circuitry from the CH1786 to the telephone line interface
must be provided in wiring that carries no other circuitry other
than that specifically allowed in the FCC rules (such as A and A1
leads).
3) Connection to phone line should be made through an RJ-11C
jack.
4) PCB traces from the modem’s RING and TIP pins to the RJ11C jack must be 0.1 inch spacing or greater to one another and
0.2 inch spacing or greater to all other traces. The traces should
have a nominal width of 0.020 inches or greater.
5) The RING and TIP PCB traces should be as short as possible
and oriented to prevent coupling other high speed or high frequency signals present on the host circuit PCB.
6) No additional circuitry other than that shown in Figure 7A or
7B may be connected between the modem module and the RJ11C jack. Doing so will invalidate the FCC approval.
7) The CH1786LC (only)requires external surge protection (see
Figure 7B).This is mandatory to maintain FCC Part 68 conveyed
approval.
8) The CH1786,the RJ-11C jack, the interfacing circuitry and all
PCB traces in between, must be contained on a PCB with a 94 V0 flammability rating.
9) The supplied FCC registration label must be applied visibly on
the outside of the product.
10) The product ’s User Manual must provide the user with instructions for connection and use as recommended in the FCC
Registration Section below.
CH1786 HANDLING AND ASSEMBLY
RECOMMENDATIONS
The CH1786 contains static-sensitive components and should only
be handled by personnel and in areas that are properly protected
against static discharge. There are two mounting techniques that
are recommended for physically connecting the CH1786 to a
PCB:1)sockets, and 2) direct soldering.
Direct Soldering.
The CH1786 may be wave soldered onto a circuit card. All
CH1786 products are hermetically sealed (except
the
CH1786NH) and will not be harmed by industry standard wave
soldering processes. Cermetek recommends against exposing the
non-hermetic CH1786NH to aqueous based rinsing processes.
Socketing.
The socketing approach to mounting eliminates cleaning and
desoldering concerns. When the socket is used, it must make a
solid connection to all pins. Failure to do so will cause unreliable
or intermittent operation. Also, steps should be taken to assure
that the module remains tightly seated in the socket after the end
product is shipped. Cermetek recommends socket CES-150-01-TS by Samtec, 50 pin strip socket.
Figure 7A. PSTN Line Interface for CH1786 Family (except CH1786LC and CH1786NH).
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
9
Figure 7B. PSTN Line Interface for CH1786LC and CH1786NH only.
FCC REGISTRATION
Telephone Company Procedures: The goal of the
All products in the CH1786 family are registered with the FCC
(Federal Communications Commission) under Part 68. To
maintain the validity of the registration, you must serve notice
to the end user of the products of several restrictions the FCC
places on the modem and its use.
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.
In addition to restriction notification, the FCC requires that
Cermetek make all repairs to all products in the CH1786
family. If repairs are necessary after installation of the
CH1786 in the end product and the end product has been
delivered to theend user, the end product must be returned to
the end product supplier where the CH1786 can be removed
and then forward to Cermetek for repair. The following notice
is recommended and should be included in the end product’s
user manual.
FOR YOUR USER’S MANUAL
The 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 telephonecompany-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
Jacks. (Name of applicant) attests that the network interface
plugs or jacks used on this equipment comply with and will
continue to comply with the mechanical requirements specified
in Part 58, 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.
2000 Cermetek Microelectronics, Inc.
In certain circumstances, it may be necessary for the
telephone company to request information from you
concerning the equipment which you have connected to
your telephone line.
Upon request of the telephone
company, provide the FCC registration number and the
ringer equivalence number (REN); both of these items are
listed on the equipment label. The sum of all of the REN’s
on your telephone lines should be less than five in order to
assure proper service from the telephone company. In
some cases, a sum of five may not be useable on given line.
Consult your telephone provider.
If Problems Arise: If any of your telephone equipment is not
operating properly, you should immediately remove it from
your telephone line, as it may cause harm to the telephone
network. If the telephone company notes a problem, they
may temporarily discontinue service. When practical, they
will notify you in advance of this disconnection. If advance
notice is not feasible, you will be notified as soon as
possible.
When you are notified, you will be given the opportunity to
correct the problem and informed of your fight to file a
complaint with the FCC. Contact your local telephone
service provider if you have nay questions about your phone
line.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
10
In the event repairs are ever needed on the (insert your product
name),they should be performed by (insert your company name)
or an authorized representative of (insert your company name).
For information contact:(insert your company address).
DEFAULT STATUS, PERFORMANCE, AND SPECS
The following is a summary of the Default Configuration
Profile installed by Cermetek Microelectronics, Inc prior to
delivery of the CH1786.
Async mode selected
2400bps
Bell 212A operation at 1200bps
Even parity
Auto answer enabled (Disabled on CH1786NH)
Command echo ON
All result codes enabled –extended
Wait for dial tone before dialing =2 seconds
Detects busy signal
Full word result codes
Pulse dial make/break ratio =39/61
DSR enabled
Modem enabled DTR (Disabled on CH1786NH)
DCD enabled (Disabled on CH1786NH)
Speaker enabled but off when receiving carrier
Speaker volume set to medium
Local modem will grant RDL request from remote modem
Guard tones disabled
Minimum DTR pulse width =0.1 seconds
Ring count =01 (CH1786)
Escape code character =43
Carriage return character =13
Line feed character =10
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
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
11
Table 7. CH1786 System Data Mode Compatibility Specifications
Table 8. CH1786 Electrical Specifications
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
12
Table 9. CH1786 Electrical Specifications
Parameter
Off Hook Impedance
Trans Hybrid Loss
Ring Voltage Loop
Minimum
20
Typical
Maximum
Units
Ohm
dB
Vpp
25
110V
250V
Line Loop Current – (Off-Hook)
Return Loss @ 1000 Hz
Ring Frequencies
Receiver Insertion Gain
Transmit Power
First Character After Reset
Inter Character Delay
-0.5
0.5
20
20
15
40
0.0
-9.5
1.0
50
Command Delay
100
200
Minimum Reset Pulse Duration
Parameter
Tone 2 nd Harmonic Distortion
100
mA
dB
Hz
dBm
dB
sec
msec
+0.5
5
msec
10
msec
Comments
600 Ohm, RXA, TXA
On 48VDC line voltage
for sustained periods
600 Ohm
600 Ohm – Data Mode
Delay
Between all command
characters
Between all AT
commands
If user supplied
Table 10. Other Performance Specifications
Min.
Typ.
Max Unit
Comments
s
-35
dB
HYB enabled into 600Ω
DTMF Twist (Balance)
3
DTMF Tone Duration
50
Pulse Dialing Rate
8
10
dB
255
ms
95 ms default
20
pps
10pps default
Pulse Dialing Make/ Break
39/61
%
US, Canada default
Pulse Dialing Make/ Break
33/67
%
UK, Hong Kong
ms
789 ms default
Pulse Interdigit Interval
700
3000
Guard Tone Frequency
550
Hz
Referenced to High Channel Transmit
Guard Tone Amplitude
-6
dB
Referenced to High Channel Transmit
Guard Tone Frequency
1800
Hz
Referenced to High Channel Transmit
Guard Tone Amplitude
-9
dB
Referenced to High Channel Transmit
High Channel Transmit Amplitude
-1
dB
Referenced to Low channel, Guard tone
enabled
Guard Tone 2
nd
Harmonic Distortion
Call Progress Passband Frequency
Wait Time for Dial tone
-40
dB
120
620
Hz
2
255
sec
Two second default
dB
Tr = 600 Ω + 2.16 µ F
Return loss @ 1000 Hz
30
Table 11. Analog Characteristics
Name
Type
SPK
O(DF)
2000 Cermetek Microelectronics, Inc.
Characteristic
Minimum Load
Maximum capacitive Load
Output Impedance
Output voltage
D.C. Offset
Value
300Ω
0.01µ
10Ω
2.5 + 1.6V
<20mV
Document No. 607-0004 ECN 8176 Rev. H (03/00)
13
Table 12. Summary CH1786 Family of Products
Summary of Features
Model
CH1786LC
CH1786NH
CH1786
CH1786ET
CH1786FX
Full function, Voice/ Inject, FCC Part 68 Approved, UL 1950
Listed, Hermetic
Full Function, No Voice/Inject, FCC Part 68 Approved, NonHermetic, UL1950 Listed
Full Function, NVRAM, FCC Part 68 approved, UL1950 Listed,
Hermetic
Full Function, NVRAM, Zero Power Option, FCC Part 68
Approved, UL1950 Listed, Hermetic
Full Function + FAX, NVRAM, FCC Part 68 Approved,
Hermetic, UL1950 Listed.
Operating Temperature
0° C to 70°C
0° C to 70°C
0° C to 70°C
-40° C to 85°C
0° C to 70°C
Currently, both UL1459 and UL1950 Listed versions are available. Effective 31 May 2000, the higher
performance UL1950 versions will become standard. Additionally, effective 31 May 2000, the combined data +
FAX functions will become standard on the CH1786 thereby obsoleting the CH1786FX.
Figure 8. CH1786 Physical Dimensions and Pin Functions
PACKAGE CONNECTION TABLE
1.
2.
3.
4.
5.
6.
PIN NO.
FUNCTION
PIN NO.
FUNCTION
1
2
3
4
5
6
7
8
9
10
11
RING
TIP
RXA
TXA
SPK
NC
NC
SLEEP
NC
TXD
RXD
12
13
14
15
16
17
18
19
20
21
22
V/D
DTR
DSR
RI
CTS
DCD
HS
VCC
GND
RST
NC
All dimensions are in inches.
Case dimensions are nominal + 0.02 inches.
Pin length is nominal + 0.03 inches.
Cermetek recommends that 0.04 inch diameter plated through holes are used with 0.060 inch diameter pads.
Pin spacings are nominal.
CH1786NH has four 15mil round, 15mil high standoffs on the bottom of the package.
*If a low profile version of the CH1786 is required, please see the CH2000.
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, no responsibility is assumed by Cermetek 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.
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
WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
2000 Cermetek Microelectronics, Inc.
Document No. 607-0004 ECN 8176 Rev. H (03/00)
14