ETC CH1786

CH1786 Family of Ultra Small 2400bps Modems
INTRODUCTION
FEATURES
• Supports Standards
212,and Bell 103
The CH1786 family of modems are 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 (1.01 ”x
1.27 ”x 0.52 ”). 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.
CCITT
V.22bis,V.22,Bell
• FCC Part 68 approved and DOT CSA CS-03 Part I
approvable
• UL 1950 and CSA C22.2 950 Listed
• UL File Number: E104957
• 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
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 approvable and can
be approved in other countries that require 1500VAC
RMS isolation requirements per UL 1950 Edition 3.
• Automatic adaptive
equalization
and
fixed
compromise
• Size: 1.01 ”x 1.27 ”x 0.52 ”(nominal)
• NVRAM allows storage of custom configurations
and telephone numbers
The CH1786 family of modems operate off a single 5volt 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.
CH1786 FAMILY
CH1786
NVRAM, Voice/ Inject,
Operating Temperature:
0°C to +70°C
Hermetic,
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.
2003 Cermetek Microelectronics, Inc.
Figure 2. Voice/ Data Port Control
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Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
DESCRIPTION OF FUNCTIONAL BLOCKS
AND DISCUSSION OF BASIC OPERATIONS
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.
Figure 1 contains a functional block drawing of the
CH1786. The CH1786 is a highly integrated, fullfunction modem, comprised of a modulator/
demodulator, controller, NVRAM and an FCC Part 68
approved and UL 1950/CSA C22.2 950 listed PSTN
line interface.
Serial Host Interface. The serial interface is a V.24
(EIA-232) compatible interface. Ten Bits total: 1 start
bit, 1 stop bit, and eight data bits which can be either
eight bits with no parity or seven odd or even with
parity. The start bit is LOW going. RXD and TXD
data is non-inverted. See pin description in Table 2.
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.
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, in turn, 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.
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.
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.
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.
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.
Speed and Parity Selection. Prior to call initiation,
the host controller trains the modem to the host
speed (2400,1200 or 300bps) and parity (odd, even,
mark, space, or none) via a host-initiated training
sequence. This training also sets the speed of the
data for originate calls.
The CH1786 will
automatically adjust to the originator’s speed when
answering calls.
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 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.
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.
2003 Cermetek Microelectronics, Inc.
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
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CH1786 Family of Ultra Small 2400bps Modems
pin becomes active. The CH1786ET products can
thus be powered down to zero.
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.
Table 1. Connection Rates.
Answering
Connection Rate Resulting
Modem Initial
When Calling Modem Initial
Trained Rate
Rate Is:
300
1200
2400
300
300
1200
1200
1200
300
1200
1200
2400
300
1200
2400
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 &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 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.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
during operation on nominal phone lines. In addition,
automatic adaptive equalization in the receiver
minimizes the effects of inter symbol interference.
Figure 3. Zero Power Operation.
Referring to Figure 3, the controller activates the relay
switch, supplying power (+5V) to the CH1786ET. In
this configuration, the ring signal is used to “wake up”
the CH1786ET when the CH1786ET is in the power
down state.
The pins of the CH1786ET 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 during power down.
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.
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.
NOTE
A 2400-baud connection rate will only result if both
modems are initially set at 2400 baud.
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.
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
2003 Cermetek Microelectronics, Inc.
Power Supply. The CH1786 modem module is a
complex set of sub-systems. During the course of
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CH1786 Family of Ultra Small 2400bps Modems
Enter: ATS7=255<CR>
Result: OK
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.
Disables data-carrier time
out
Enter: ATS10=255<CR> Disables lost-carrier time
Result: OK
out
The following command sequences illustrate
implementation of common Voice/Tone Port
applications.
1. To answer a voice call.
(a) Enter: ATH1<CR>
Result: OK
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.
(b) Drive V.INJ. HIGH to activate relay.
(c) Begin voice conversation.
2. To switch to data mode.
(a) Drive V.INJ. LOW
(b) At the originate modem:
Enter: ATX1<CR>
Result: OK
Voice/DTMF 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.
3. To disconnect (hang-up) a voice call or a data
call.
(a) Enter: ATH<CR>
Result: OK
WARNING: The CH1786 has been FCC Part 68
approved as a data modem only. Utilization of
the Voice/DTMF 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.
4. To place a call to 1234567 using the CH1786’s
DTMF tone generator.
(a) Enter: ATDT1234567;C0<CR>
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
(Refer to Figure 4):
MODEM CONTROL
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.
Figure 4. Voice/Tone Injection.
2. Initial modem training. The CH1786 must be
trained to the host ’s speed (2400,1200,300bps)
and parity (odd, even, mark, space or none).
Enter: ATS0=<CR>
Result: OK
These activities are briefly described below.
Disables auto-answer
2003 Cermetek Microelectronics, Inc.
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CH1786 Family of Ultra Small 2400bps Modems
Reset. Upon applying power to the CH1786, the
CH1786 automatically generates an internal reset
pulse. The user may 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.
<CR> represents carriage return (ASCII 13
or HEX 0D).
When entering commands to the modem, the
backspace character-control-H (ASCII 8 or HEX 08)
may be used to edit mistakes. AT and A/ may not be
edited. 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.
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’s is 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.
Enter: ATE0A<CR>
Result: OK
Modem Training Command Sequence.
The
CH1786 is trained by sending it the following
sequence:
AT Command Set. 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.
Enter: AT<CR>
Result: OK
Where: A and T may be either upper or lower case
but must be the same case.
<CR> represents carriage return
AT Command Data Rate. With the serial interface,
the rate is speed sensed for parity and format.
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 Terse (abbreviated) or Verbose
(English) status messages.
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.
Result: 0<CR> (Terse)
or
Result: <CR><LF>OK<CR><LF> (Verbose)
Where: <CR> represents carriage return (ASCII 13
or HEX 0D).
<LF> represents line feed (ASCII 10 or
HEX 0A).
X0:
X1:
X2:
X3:
X4:
After responding with an OK, the CH1786 is in idle
mode and is ready to accept additional commands.
An alternate attention sequence A/ may be sent
which behaves much like the AT sequence except
that it causes the previously entered command
specified with an AT prefix to be executed. When
given, both the AT and A/ must be in upper case
ASCII. No carriage return is needed for the A/
command.
NOTE
The CH1786 is factory set to X4, which allows all
result codes.
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 COMMAND FORMAT
Typical commands consist of three elements: the
attention sequence, the commands themselves, and
a terminating carriage return.
AT[commands]<CR>.
Where: AT represents attention sequence.
[Commands] represents command strings.
2003 Cermetek Microelectronics, Inc.
Result Codes 0, 1, 2, 3, 4 allowed
Result Codes 0, 1, 2, 3, 4, 5, 10 allowed
Result Codes 0,1, 2, 3, 4, 5, 6, 10 allowed
Result Codes 0, 1, 2, 3, 4, 5, 7, 10 allowed
Result Codes 0, 1, 2, 3, 4, 5, 6, 7, 10 allowed.
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CH1786 Family of Ultra Small 2400bps Modems
Figure 5. CH1786 Application Diagram
2003 Cermetek Microelectronics, Inc.
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Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
Table 2. CH1786 Pin Descriptions
FUNCTION
PIN
NAME
TYPE
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 RJ11C 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.
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 offhook 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. DET 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. No connect if not using the FAX option. Reserved for flow
control when using FAX option. CTS only active on CH1786 when S24=255.
17
DCD
O
DATA CARRIER DETECT. LOW indicates a data carrier from a remote modem is
detected. Must be enabled using the &C1 command.
2003 Cermetek Microelectronics, Inc.
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Received marking or binary 1
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CH1786 Family of Ultra Small 2400bps Modems
Table 2. CH1786 Pin Descriptions Continuation
PIN
NAME
TYPE
FUNCTION
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. 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
status message when it is ready to accept
commands. The CH1786 may be put into data mode
by issuing the command ATO<CR>.
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. The guard time is set by register S12.
The escape character code is set in register S2. At
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.
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:
ATD1234567<CR>
The CH1786 will stay off-hook with its carrier on after
the escape sequence is received. It will return an OK
2003 Cermetek Microelectronics, Inc.
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Result:
CH1786 Family of Ultra Small 2400bps Modems
Enter:
Result:
OK
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, permitting communication with the
distant modem.
ATDT9,1234567;<CR>
OK
Automatic Answering. The SO 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.
S0 =
S0 =
S0 =
S0 =
S0 =
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.
0 DO NOT ANSWER TELEPHONE
1 ANSWER ON RING 1
2 ANSWER ON RING 2
3 ANSWER ON RING 3
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 the need for level translation circuitry.
See Table 2 for a complete pin description.
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.
The CH1786 is controlled by sending it serial
commands over TXD and it’s status determined by
monitoring the serial status messages returned on
RXD. DTR is optionally used to reset, terminate calls
or return CH1786 to command mode.
Example: Dial 9,pause, dial number.
Enter:
ATDT9,1234567<CR>
Result: OK
Multiple commas may be used to generate integer
multiples of the specified delay time.
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.
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.
to
Fax Modes. The CH1786 Product Family supports
Send and Receive FAX. The modes and rates are
determined by the AT+F commands. Refer to Table
6A.
Multiple commas may be used to generate integer
multiples of the specified delay time.
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.
Example: Change modem from
answer mode.
Enter:
ATDT1234567R<CR>
Result: OK
original-only
Redial Last Number. The repeat command is a
convenient way to execute the previously entered
command line.
Table 4. CH1786 Register Summary.
Register
Function
S0*
Ring to Answer On
S1
Ring Count
S2
Escape Code Character
S3
Carriage Return Character
S4
Line Feed Character
S5
Back Space Character
S6
Wait for Dial tone
S7
Wait for Data Carrier
S8
Pause Time for Comma
Example: Use A/, the repeat command, to redial the
last telephone number dialed.
Enter:
A/
Result: ATDT1234567R<CR> Previous command
OK
line executed
Return to Command State. Use ; to return to
command mode offer dialing.
Example: Touch-tone dial 9, pause, dial number,
return to Command.
2003 Cermetek Microelectronics, Inc.
Page 9
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
Table 6A.
FAX Command Set Summary.
FAX Command
Function
+FCLASS=n
Select Service Class
+F<command>?
Report Active Configuration
+F<command>=?
Report Operating Capabilities
+FAA=n
Data/Fax Auto Answer
+FF
Enhanced Flow Control
+FTS=n
Stop Transmission and Wait
+FTSM=n
Transmit Data
+FTH=n
Receive Data
+FTH=n
Transmit Data with HDLC
Framing
+FRH=n
Receive Data with HDLC
Framing
+FRT=n
Receive Test Data
+FTTn=m
Transmit test Data
Table 4. CH1786 Register Summary
Continuation.
Register
Function
S9
Carrier Detect Response Time
S10
Lost Carrier to Hang-up Delay
S11
DTMF Dialing Speed
S12
Escape Code Guard Time
S14*
Bit Mapped Options Register
S16
Modem Test Options
S21*
Bit Mapped Options Register
S22*
Bit Mapped Options Register
S23*
Bit Mapped Options Register
S24
Sleep Mode Inactivity Time
S25*
Delay to DTR
S27*
Bit Mapped Options Register
S28*
Bit Mapped Options Register
Table 6B.
Dial Modifiers
P
R
Note
In Tables 4, 5, 6A-6C an * signifies parameters that
are stored in NVRAM upon receipt of the &W
command.
The CH1786LC, CH1786LCNE,
CH1786NE and CH1786NH do not contain NVRAM
and, therefore, do not support data storage after
power down. 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 website at www.cermetek.com.
T
W
;
@
!
,
0-9
A,B,C,D
Table 5. CH1786 AT Command Set Summary.
Basic
Function
Commands
AT
Attention Code
A
Answer command
A/
Repeat last Command
BN*
Communications Standard Option
D
Dial Command
E*
Off-Line Character Echo Option
Hn
Switch Hook Control Option
Ln*
Speaker Volume Option
Mn*
Speaker Control Option
On
On-Line Command
P
Pulse Dial
Qn*
Result Code Display Option
Sn
Select an S Register
Sn=
Write to an S Register
Sn?
Read an S Register
Vn*
Result code Form Option
Xn*
Result Code Set/Call Progress
Option
+++
Escape Code Sequence Pause
,
Pause
?
Returns Last addressed S Register
Yn*
Long Space Disconnect Option
Fn
On Line Echo character Option
Z
Reset
2003 Cermetek Microelectronics, Inc.
Dial Modifiers Summary.
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
Table 6C. Ampersand and Percent Commands.
Ampersand
Function
Commands
&Cn*
Data Carrier Detect Option
&Dn*
Data Terminal Ready Option
&F
Load Factory Defaults
&Gn*
Guard Tone Option
&Pn*
Make to Break Ratio Section
&Sn*
Data Set Ready Option
&Tn
Test Command Option
&V
View Active Configuration
&Wn*
Store Active Profile
&Yn*
Recall Active Profile
&Zn*
Store Telephone Numbers
Percent
Function
Commands
%Dn
DTMF Attenuation
%J
Load Secondary Factory
Defaults
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.
Page 10
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
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).
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.
The two recommended mounting
techniques for physically connecting the CH1786 to a
PCB are discussed below.
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 RJ-11C 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.
Direct Soldering.
The CH1786 may be wave
soldered. All CH1786 products are hermetically
sealed (except the CH1786LCNE, CH1786NE, and
CH1786NH) and will not be harmed by industry
standard wave soldering processes.
Cermetek
recommends against exposing the non-hermetic
CH1786LCNE, CH1786NE, and CH1786NH to
aqueous based rinsing processes.
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.
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 during shipping. Cermetek recommends using
sockets from Samtec. See Application Note # 130,
Summary of Recommended Suppliers.
6. No additional circuitry other than that shown in
Figure 7A or 7B may be connected between the
modem module and the RJ-11C jack. Doing so
will invalidate the FCC approval.
7. The CH1786LC, CH1786LCNE, and CH1786NH
(only) requires external surge protection (see
Figure 7B). This is mandatory to maintain FCC
Part 68 conveyed approval.
FCC REGISTRATION
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.
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 V-0 flammability
rating.
9. The supplied FCC registration label must be
applied visibly on the outside of the product.
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 the end 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.
10. The product’s User Manual must provide the user
with instructions for connection and use as
recommended in the FCC Registration Section
below.
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
Figure 6. Speaker Control Circuit: Optional to
allow for call progress monitoring.
2003 Cermetek Microelectronics, Inc.
Page 11
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
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).
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, subpart 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.
DEFAULT STATUS, PERFORMANCE, AND
SPECIFICATIONS
The following is a summary of the Default
Configuration Profile installed by Cermetek
Microelectronics, Incorporated, 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
Telephone Company Procedures. The goal of the
telephone company is to provide you with the best
service it can. In order to do this, it may occasionally
be necessary for them to make changes in their
equipment, operations or procedures.
If theses
changes might affect your service or the operation of
your equipment, the telephone company will give you
notice, in writing, to allow you to make any changes
necessary to maintain uninterrupted service.
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 right to file a complaint with the FCC. Contact
your local telephone service provider if you have nay
questions about your phone line.
2003 Cermetek Microelectronics, Inc.
Page 12
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
Figure 7.
CH1786 Family of Ultra Small 2400bps Modems
PSTN Line Interface for all CH1786 Products.
1. Currently Limiting PSTN Protection Line
Device.
Currently limiting devices are mandatory to meet
UL safety standards. To maintain conveyed FCC
Part 68 approval, the current limiting components
identified as F1 and F2 in dashed Box #1 must
also survive FCC Part 68 surge testing. Refer to
Cermetek Application Note #126, Supplemental
PSTN Line Protection, for more details. Refer to
Application Note # 130, Summary of Recommend
Suppliers, for a list of suppliers and associated
part numbers.
A. A Polyfuse (rated at 0.15 amps) is preferred
because it resets automatically upon removal
of the current flow. Non-resettable devices
are also acceptable. Refer to Application Note
#130 for a complete list of recommended
vendors and associated part numbers.
B. Resistors (10Ω carbon film or 1/8 watt
minimum) may be used in Canada, as Canada
has no requirements that PSTN equipment be
operational after a Type B surge test.
C. Although CSA CS-03 Part 1 (Canada) follows
the requirements of FCC Part 68 (USA),
Cermetek recommends contacting DOT
(Canada) and/or a certified independent lab to
verify compliance. For Canada, use either
10Ω resistors (carbon film or SMD parts 1/8
watt minimum) as described in paragraph B
above.
2. Over Voltage and Lightning Protection.
A. Surge Protection is provided by internal
circuitry contained within all CH1786 Products
except the CH1786NH (see Figure 7). No
additional external components are required to
maintain conveyed FCC Part 68 approval for
all
CH1786
Products
(excluding
the
CH1786NH).
2003 Cermetek Microelectronics, Inc.
Page 13
B. For CH1786NH, the required surge protection
(identified as D1 in dashed Box 2) must be
supplied externally.
The purchaser must
include some form of surge protection as
described herein to maintain conveyed FCC
Part 68 approval.
C. In most environments, 2 terminal surge
suppressors are adequate.
For severe
environments, use an external 3 terminal
device with an earth ground.
3. EMI/RFI Suppression.
No external EMI/RFI noise suppression circuitry is
required to maintain conveyed FCC Part 68
approval. However, additional suppression, if
required for other reasons, may be added as
described below in Sections 3A-3B without
adversely affecting FCC Part 68 approval.
A. To provide adequate EMI/RFI suppression,
the capacitor/inductor network contained in
dashed Box #3 should be located as close to
the RJ11 Jack as possible. Further, this
network should be provided with an excellent
ground path to the chassis.
B. Capacitors C1 and C2 should not exceed
0.005µf. They must have a rating of 1.5KV
and typically are 0.001µf ± 20%. Inductors L1
and L2 may be either individual inductors or a
dual inductor. Refer to Application Note #130
for a complete list of recommended vendors
and associated part numbers.
For UL
applications, choose capacitors and inductors
that are UL 1950 listed. The actual values of
the components used may vary depending on
the end product design.
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
Table 7. CH1786 System Data Mode Compatibility Specifications.
Specification
Parameter
Specification
2400, 1200 600 bps character
Receive Carrier
Originate 2400Hz ± 7Hz
asynchronous.
Frequencies
Answer 1200Hz ± 7Hz
0-300 bps asynchronous
V.22 bis, V.22,
212A
Asynchronous
Speed
TXD may differ +1%, -2.5%
Bell 103
Answer
‘space’ 2020Hz ±
Range
from modem output. Offsets
7Hz
will be corrected by adding/
Answer ‘mark’ 2225Hz ±
deleting stop bits.
7Hz
Originate ’space’ 1070Hz ±
7Hz
Originate ‘mark’
1270Hz ±
7Hz
Asynchronous Format
8,9,10 bits, including start,
Receiver
OFF to ON threshold –43
stop, parity.
Sensitivity
dBm
ON to OFF threshold –48
dBm
Telephone Line Interface
Two-wire full duplex over
Billing Delay
2.0 to 3.0 seconds (Ta=25°C)
public switched network. Onchip 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,
Originate ‘mark’
1270Hz ±
busy, ring-back, modem
.01%
answer tone and voice).
Answer
‘space’ 2020Hz ±
Computer
IBX PC/XT/AT bus
.01%
Interface
compatible with an
Answer
‘mark’
2225Hz ±
8250/16450/16550A UART
.01%
as a serial controller.
Parameter
Asynchronous
2003 Cermetek Microelectronics, Inc.
Page 14
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
Table 8. CH1786 Electrical Specifications.
Parameter
ICC Off Hook
Nominal Operating Current when modem is OFF Hook
50
Ma
x.
5.2
5
75
ICC On Hook
Nominal Operating Current when modem is ON Hook
25
50
mA
10
mA
VCC
ICCPD
Description
Positive Supply Voltage- Noise less than 50mV
Min.
Typ.
4.75
5.0
Power Down Current
Units
V
mA
VIH
High Level Input Voltage*
2
V
VIL
Low Level Input Voltage*
-0.3
0.8
V
IIN
Input Leakage Current (TXD, DTR, RTS)
15
10
0
uA
ILO
CP
Leakage Current DCD, HS, RXD, SLEEP, DSR
Capacitive Lead (TXT, DTR, RST)
10
10
uA
pF
VT+
Positive Hysteresis Threshold for RESET pin
2.5
V
VT-
Negative Hysteresis Threshold for RESET pin
1.8
V
VOH
High Level (IOH = 0.5mA)*
VOL
Low Level (IOL = 1.6mA)*
2.4
V
0.6
V
Test conditions: VCC = 5V ± 10%, Temp = 0°C to 70°F (unless otherwise stated).
*Output Load = 50 pF ± one TTL.
Parameter
Off Hook Impedance
Table 9. CH1786 Electrical Specifications.
Minimum
Typical
Maximum
Units
20
Ohms
Trans Hybrid Loss
Ring Voltage Loop
25
110V
dB
600 Ohm, RXA, TXA
250V
Vpp
On 48VDC line voltage for
sustained periods
100
mA
Line Loop Current-(OffHook)
Return Loss @ 1000Hz
15
dB
Ring Frequencies
40
Hz
Receiver Insertion Gain
20
-0.5
Transmit Power
0.0
Comments
+0.5
-9.5
dBm
600 Ohm
600 Ohm- Data Mode
dB
First Character After Reset
0.5
1.0
Inter Character Delay
20
50
msec
Command Delay
100
200
msec
Between all command
characters
Between all AT commands
Minimum Reset Pulse
Duration
10
msec
If user supplied
2003 Cermetek Microelectronics, Inc.
5
Page 15
sec
Delay
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
CH1786 Family of Ultra Small 2400bps Modems
Table 10. Other Performance Specifications.
Parameter
Minimum
Tone 2nd Harmonic
Distortion
DTMF Twist (Balance)
Maximum
Units
-35
dB
3
DTMF Tone Duration
50
Pulse Dialing Rate
8
Pulse Dialing Make/
Break
Pulse Dialing Make/
Break
Pulse Interdigit Interval
Typical
10
Comments
HYB enabled into 600Ω
dB
255
ms
95ms default
20
pps
10pps default
39/61
%
US, Canada default
33/67
%
UK, Hong Kong
ms
789ms default
Referenced to High Channel
Transmit
Referenced to High Channel
Transmit
Referenced to High Channel
Transmit
Referenced to High Channel
Transmit
Referenced to Low channel,
Guard tone enabled
700
3000
Guard Tone Frequency
550
Hz
Guard Tone Amplitude
-6
dB
Guard Tone Frequency
1800
Hz
Guard Tone Amplitude
-9
dB
High Channel Transmit
Amplitude
Guard Tone 2nd
Harmonic Distortion
Call Progress
Passband Frequency
Wait Time for Dial tone
-1
dB
-40
dB
120
620
Hz
2
255
sec
Two second default
dB
Tr=600Ω + 2.16 µF
Return loss @ 1000Hz
Name
SPK
2003 Cermetek Microelectronics, Inc.
30
Table 11. Analog Characteristics.
Type
Characteristic
O(DF)
Minimum Load
Maximum Capacitive Load
Output Impedance
Output voltage
D.C. Offset
Page 16
Value
300Ω
0.01µ
10Ω
2.5± 1.6V
<20mV
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
PIN NO.
1
2
3
4
5
6
7
8
9
10
11
Figure 8.
CH1786 Family of Ultra Small 2400bps Modems
Table 12. CH1786 Pin Functions.
PACKAGE CONNECTION TABLE
FUNCTION
PIN NO.
RING
12
TIP
13
RXA
14
TXA
15
SPK
16
NC
17
NC
18
SLEEP
19
NC
20
TXD
21
RXD
22
FUNCTION
V/D
DTR
DSR
RI
CTS
DCD
HS
VCC
GND
RST
NC
CH1786 Physical Dimensions.
2003 Cermetek Microelectronics, Inc.
Page 17
Document No. 607-0004 Revision L1 (06/03)
Cermetek Microelectronics, Inc.
Table 13. Summary CH1786 Family of Products.
Summary of Features
Model
CH1786
CH1786ET
CH1786FX
CH1786FXNE
CH1786LC
CH1786LCNE
CH1786NE
CH1786NH
CH1786 Family of Ultra Small 2400bps Modems
Full function, Voice/Inject, NVRAM, FCC Part 68 approved, UL 1950
Listed, Hermetic
Full function, Voice/Inject, NVRAM, Zero Power Option, FCC Part 68
Approved, UL 1950 Listed, Hermetic
Full function, FAX, Voice/Inject, NVRAM, FCC Part 68 approved, UL
1950 Listed, Hermetic
Full function, FAX, Voice/Inject, NVRAM, FCC Part 68 approved, UL
1950 Listed, Non-Hermetic
Full function, Voice/Inject, FCC Part 68 Approved, UL 1950 Listed,
Hermetic
Full function, Voice/Inject, FCC Part 68 approved, UL 1950 Listed,
Non-Hermetic
Full function, Voice/Inject, NVRAM, FCC Part 68 approved, UL 1950
Listed, Non-Hermetic
Full function, FCC Part 68 Approved, Non-Hermetic, Listed UL 1950
Operating
Temperature
0°C to 70°C
-40°C to 85°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
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.
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/
2003 Cermetek Microelectronics, Inc.
Page 18
Document No. 607-0004 Revision L1 (06/03)