CH2056/TBR/ETBR
–
V.90 / 57,600bps/TBR21
CH1799/TBR/ETBR
–
V.34bis / 33,600bps/TBR21
CH1794
–
V.32bis / 14,400bps
FEATURES
The HS Modem family is pin compatible with
Supports V.90, V.34bis, V.34, V.32bis, V.32,
Cermetek’s low cost CH1786 V.22bis, 2400bps
V.22bis, V.22A/B, V.23, V.21, Bell 212A and 103.
modem family. Each module in the HS Modem family
is a self-contained modem and is FCC Part 68
CH2056 supports V.80 Synchronous operation.
approved
and
Canadian
DOT
approvable.
Error correcting: V.42 LAPM, MNP 2-4 and
Additionally,
the
CH1799TBR/ETBR
and
the
MNP10.
CH2056TBR/ETBR products meet the European
Data Compression: V.42bis and MNP 5
TBR21 requirements.
MNP10 Data through put enhancement for cellular
These ultra small modules are designed for PCB
operation.
through-hole mounting and are 1.35” x 1.38” x 0.55” in
DTE serial interface with speeds up to 230.4kbps
size. The HS Modem family requires only two external
(CH2056), 115.2 (CH1799) or 57.6kbps (CH1794).
interfaces: a ITU-T V.24 serial interface for direct
access to a UART, and a Tip and Ring RJ-11C Jack
Automatic baud rate adaptability utilizing speed
for the PSTN line connection. The HS Modem can be
sensing, flow control and data buffers.
controlled with industry standard AT commands and is
Send & Receive FAX class 1, Group 3 supported.
compatible with available industry communication
Serial V.24, 5 volt interface.
software.
NVRAM directory and stored profiles.
AT Command structure, with extensions.
DESCRIPTION OF FUNCTIONAL BLOCKS
Built-in DAA with 1500 VAC RMS isolation 2122V
AND DISCUSSION OF BASIC OPERATIONS
peak surge protection.
Figure 1 contains a functional block drawing of the HS
UL 1950 and CSA C22.2 950 Recognized
Modem family of products. Each HS Modem product
(E104957).
consists
of
a
serial
interface
buffer,
modulator/demodulator, modem controller with error
Leased Line version available CH1799LL
correction and data compression, non-volatile RAM
FCC part 68 Approved/DOT CSA CS-03 Part I
and a DAA.
Approvable.
+5 Volt operation with zero power option
Small size: 1.35” x 1.38” x 0.55”.
Pin compatible with low speed/low cost CH1786
TBR21
compliant
versions
available:
CH1799TBR/ETBR and CH2056TBR/ETBR.
INTRODUCTION
The CH2056, CH1799 and CH1794 (HS Modem
Family) are industrial grade high-speed modem
modules. Each HS Modem product supports a range
of modem standards and speeds from 300bps to
14,400bps, 28,800bps, 33,600bps or 57,600bps. By
using built in compression algorithms the operation
speed can be expanded to the maximum DTE rate of
Figure 1. Functional Block Diagram of HS Modem
57.6kbps for the CH1794, 115.2kbps for the CH1799
Family.
and 230.4kbps for the CH2056. A choice of error
correcting schemes is available including MNP 10 for
cellular telephone applications. The HS Modem family
Serial Host Interface Buffer. The HS Modem utilizes
supports Send and Receive FAX.
The CH1799LL
a serial V.24 EIA 232-E 5V interface to control the
operates exclusively on non-voltage bearing leased
modem. The HS Modem products can communicate
line.
over the serial interface with the Data Terminal
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0003 Revision K6 (08/04)
Cermetek Microelectronics, Inc.
Equipment (DTE) at a fixed speed regardless of the
compliance, and also optionally for FCC Part 15
carrier line modulation speed (DCE) of the PSTN
compliance, these two pins must be routed through an
modem connection. This eliminates the need to have
external network such as that briefly described in
the DTE step up or step down in speed based on the
Figure 6A and described in more detail in Cermetek
in-coming or out-going PSTN communication data
Application Note # 126.
rate. Hence, the DTE can train the CH2056, to say
56kbps, and talk to a slower in-coming data
Each HS Modem product comes with FCC Part 68
connection at say, 2400bps without changing host
approval and is shipped from the factory with an FCC
speed. Conversely, the host DTE trained at 14.4kbps
Label indicating registration number and ringer
can also communicate with the modems at higher
equivalent. This label should be prominently displayed
speeds, say 28.8kbps.
This is accomplished by
on the end product. With the exception of the U.S.,
invoking internal automatic data flow control. The HS
most countries (including Canada) require submission
Modem family has a resident buffer to allow for this
of the final product or system containing the HS
auto baud operation.
Modem to the appropriate governing regulatory
agency for approval. Typically this is accomplished by
Non-Volatile RAM (NVRAM).
NVRAM can store
submitting the final end product to an independent test
user-customized
configurations.
The
AT&Wn
house or consultant for evaluation.
The test
command will store the active modem configuration in
house/consultant then forwards the test results and
one of two NVRAM locations as selected by an n of 0
applicable documents to the regulatory agency.
or 1. The AT&Yn command selects one of the stored
Contact Cermetek for a list of suggested consultants.
modem configurations to be automatically recalled and
made active upon reset or power up.
The ATZn
Modulation/Demodulation/Error
Correcting
and
command immediately recalls and activates a stored
Data Compression. These functions are provided by
configuration. See Tables 6A and 6B for storable S-
an industry standard modem chip set which has been
Registers and Commands.
adapted for use with the HS Modem family.
The
Modulation/Demodulation
scheme
supports
the
The NVRAM can save up to four telephone numbers,
industry modem standards listed below.
with up to 31 digits or modifiers in each telephone
number.
The AT&Zn=s command will store s, the
SUPPORTED MODULATION STANDARDS
telephone number dial string. The ATDS=n command
Bell 103
ITU-T V.22
will cause the modem to dial one of the four stored
Bell212A
ITU-T V.22bis
telephone numbers. The NVRAM storage location for
ITU-T V.32
the four telephone numbers is selected by an n of 0, 1,
ITU-T V.32bis
2, or 3.
ITU-T V.34
ITU-T V.34bis
Telephone Line Interface or DAA. High performance
ITU-T V.90
modems are extremely sensitive to DAA (Data Access
Arrangement) performance. The difference between a
The HS Modem supports V.42 LAPM, MNP 2-4, MNP
good modem and a fair one is in the DAA
10 error correcting protocols.
The CH1794 uses
performance.
The HS Modem family includes a
MNP5
data
compression
techniques
and
the
unique low distortion DAA designed for optimal
CH1799/CH2056 uses V.42bis data compression,
performance over all PSTN line conditions thereby
allowing data transmission rates of up to a maximum
achieving the most reliable and best performance
of
57.6kbps/115.2kbps/230.4kbps,
respectively.
PSTN connections.
These high DTE data rates are supported by the HS
Modem serial interface via its auto baud capability.
The HS Modem family is designed to meet North
Note that the maximum speed attained is limited by
American telephone standards as set by the FCC Part
the maximum speed available from the DTE.
68 (USA) and CSA CS-03 Part I (Canada). Among the
more critical parameters, the PSTN line interface is
The resident Modulator/Demodulator supports line
designed to meet 1500 VAC RMS isolation and
equalization and forward error correction.
provide 2122V peak surge protection. Consequently,
the HS Modem family of products satisfies U.S. and
Canadian
requirements,
and
will
meet
other
international
approval
agency
requirements
that
IMPORTANT NOTE
specify these levels of isolation.
The TBR/ETBR
The
V.90
standard
prescribes
56kbps
variants also meet the European TBR21 requirements.
downlink and 33.6kbps uplink. Consequently,
two V.90 modems connected back-to-back will
Pins 1 and 2 function as both input and output
send at 33.6kbps.
connections to the PSTN. To maximize field reliability
in hostile environments, for Canadian approval, for UL
2004 Cermetek Microelectronics, Inc.
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Cermetek Microelectronics, Inc.
CONNECTING TO THE HOST UART
Modem is powered down. The internal blocking diode
Since a modem communicates data serially and most
provides supply isolation.
host products handle data in a parallel format, a UART
is needed to make parallel-to-serial and serial-to-
The pins of the HS Modem will be in an undefined
parallel translations.
state when powered is switched off.
This must be
taken into consideration to assure that no unwanted
signals are presented to the HS Modem during power
SUPPORTED FEATURES
down.
AT Command Set. The HS Modem supports the AT
Command set with extensions and can operate with
industry standard communication software. The AT
Commands are compatible with TR302.2/88-08006.
Serial Host Interface.
The HS Modem family
operates in asynchronous mode and supports a 5V,
RS232- like interface called V.24 (EIA-232-E). The HS
Modem supports a full RS-232C/V.24 serial interface.
Signal levels are TTL rather than RS-232C level
compatible, which allows direct connection of the HS
Modem to the host’s UART without level translating
circuitry.
See Table 3 for a complete set of pin
descriptions.
The modem is controlled by sending serial commands
over TXD and by monitoring serial status messages
returned on RXD. All other serial interface lines may
be utilized for the convenience of a particular
application but are not required by the modem.
Unused outputs from the HS Modem should be left
unconnected.
Unused inputs should be tied to the
Figure 2. Zero Power Operation.
proper logic level. See Table 3.
Power Supply. The HS Modem module is a complex
Speaker Interface.
The SPK output reflects the
set of sensitive subsystems.
During the course of
receiver analog input and provides a signal that can be
normal operation, the HS Modem decodes analog
used to monitor call progress. The SPK signal can
signals from the telephone line that are in the millivolt
drive a 300-ohm load directly.
Typically, the SPK
range. Steps must be taken by the user to guarantee
signal is input into an audio power amplifier and the
that power supply noise on all supply lines, including
amplifier, in turn, drives the speaker coil. The speaker
ground, does not exceed 25mV peak to peak.
If
is activated with the ATMn command. The speaker
necessary, use dedicated power and ground planes.
volume is adjusted using the ATLn command; where n
Failure to provide such operating conditions could
is 0, 1, 2, or 3. Increasing numbers correspond to
cause the HS Modem to malfunction or to function
higher volume.
Figure 3 indicates one method of
erratically.
driving an external 8-ohm speaker.
The HS Modem family requires +5V ±5% supply. It is
Zero Power Mode. If an application calls for zero
recommended that bypass capacitors be placed on the
power during standby periods, the power may be
power supply as close to the HS Modem’s supply input
switched off using external circuitry and then reapplied
pins as practical. It is recommended that a 10 µF or
when the HS Modem’s RI pin becomes active. The
greater tantalum capacitor in parallel with a 0.1 µF
HS Modem can thus be powered down to zero.
ceramic capacitor be used.
The user must also
provide shielding from nearby sources of EMI, such as
Referring to Figure 2, the controller activates the relay
relays, motors and other power supplies.
switch, supplying power (+5V) to the HS Modem. In
this configuration, the ring signal is used to “wake up”
Automatic Speed/Format Sensing. The HS Modem
the HS Modem when the HS Modem is in the power
supports both Command and Data modes of
down state.
operation.
The internal structure of the RI pin consists of an open
The HS Modem can automatically determine the
collector opto transistor with a 30k ohm pull-up through
speed and format of the data sent from the DTE over
a blocking diode to 5V. The user should apply his own
the serial interface; and can sense the following broad
pull-up resistor to an active 5V source when the HS
range of speeds:
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0003 Revision K6 (08/04)
Cermetek Microelectronics, Inc.
CH1794
300, 600, 1200, 2400, 4800, 7200,
for an alternative voice/tone implementation that
9600, 12000, 14400, 19200, 38400, and
utilizes dual supply operational amplifiers.
57600bps.
CH1799
300, 600, 1200, 2400, 4800, 7200,
Table 2. HS Modem Auto Configuration Based on
9600, 12000, 14400, 16800, 19200,
DTE Configuration .
21600, 24000, 26400, 28800, 38400,
DTE Configuration
HS Modem
57600, and 115200bps.
Configuration
CH2056
300, 600, 1200, 2400, 4800, 7200,
7 mark
7 none
9600, 12000, 14400, 16800, 19200,
7 space
8 none
21600, 24000, 26400, 28800, 38400,
8 mark
8 none
57600, 115200, and 230400bps.
8 space
8 even
The data formats in Table 1 are recognized by the HS
Modem family of products.
Table 1. Data Formats Recognized by HS Modem
Family.
No. of
Character
Data Length
Stop
Length
Parity
(No. of Bits)
Bits
(No. of Bits)
None
7
2
10
Odd
7
1
10
Even
7
1
10
None
8
1
10
Odd
8
1
11*
Even
8
1
11*
*11 bit characters are sensed, but the parity bits are
Figure 3. Speaker Control Circuit.
stripped off during data transmission in Normal and
Error Correction modes.
All HS Modem products are designed with pin T1
The HS Modem can sense data with mark or space
coupled directly to the internal DAA. When using the
parity and configures itself as described in Table 2.
HS Modem in data mode, T1 should float and be
disconnected from any potential signal because any
The HS Modem is trained to a selected speed with an
signal on T1 during data operation will affect the HS
AT<CR> training sequence. Thus, the DTE to modem
Modem’s output. If T1 is being asserted from another
serial interface speed can be set independent of the
application, use a relay or zero impedance switch to
DCE or line carrier connecting speed (with minor
disconnect T1 when in data mode.
restrictions, see the AT+ MS command). This allows
greater flexibility when selecting DCE line carrier
When voice and data are both being used, and the T1
modulation speed thereby affording the user with
pin is active, it is typical for voice communication to
optimum data throughput performance. To maximize
precede data communication.
In this case, the
effective modem data throughput speed, the DTE to
following commands should be used to configure the
modem serial interface speed should be set to the
HS Modem to allow for full utilization of the Voice/Tone
highest speed available without invoking the use of the
injection feature.
These commands disable auto-
HS Modem’s built-in flow control.
Although flow
answer and eliminate hang-up due to lack of carrier
control facilitates communication with higher speed
signal.
modes by the DTE, use of flow control causes an
overall throughput data rate penalty.
1. Enter: ATS0=0<CR>
2. Enter: ATS7=255<CR>
Voice/Tone Injection Port. The HS Modem Family
3. Enter: ATS10=255<CR>
provides pin T1 to allow the user to share the PSTN
line interface associated with the modem for voice and
The
following
command
sequences
illustrate
DTMF applications.
Figure 5 contains a schematic
implementation
of
common
voice/tone
port
which uses a 5 Volt single supply operational amplifier
applications.
and indicates one possible configuration for voice/tone
utilization.
1. To answer a voice call:
(a) Enter: ATH1<CR>
Refer to Cermetek Application Note #170, 2-4 Wire
(b) Switch local voice source into T1
Converter for Use with CH179X and CH2056 Modems,
(c) Begin Voice Conversation
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0003 Revision K6 (08/04)
Cermetek Microelectronics, Inc.
2. To switch to data mode, switch local voice source
The escape sequence consists of a “guard time” (a
from T1:
period where no characters are sent to the modem),
(a) At the Originate Modem, enter: ATX1<CR>
followed by 3 escape characters, followed by a second
(b) At the Answer Modem, enter: ATA<CR>
guard time. At power-up, the guard time is set to 1
second, and the escape character is set as ”+.” Note
3. To disconnect (hang-up) a voice call or data call:
that a 50 msec delay is required between escape
(a) Return to control mode by entering: +++
characters. These two parameters can be modified
(b) Enter: ATH<CR>
via registers S2 and S12, respectively.
4. To place a voice call using the HS Modem DTMF
The HS modem will stay off-hook with its carrier on
facilities:
after the escape sequence is received.
The HS
(a) Enter: ATDT1234567<CR>
Modem will return an OK status message when it is
Where 1234567 is the phone number
ready to accept commands. To put the HS Modem
(b) Then switch to local voice source
back into data mode, issue command ATO<CR> .
MODEM CONTROL
THE COMMAND FORMAT
The HS Modem may be controlled by sending serial
HS Modem commands consist of three elements:
ASCII command sequences. The commands are sent
1. The attention sequence,
to the modem serially on the TXD pin. After execution
2. The commands themselves and
of a received command, the modem returns a serial
3. A terminating carriage return.
status message that completion status. Refer to Table
5A, 5B and 5C for a complete list of status messages.
Enter:
ATDT1234567<CR>
Result:
Modem goes off-hook and tone dials phone
number 1234567.
MODEM STATES
The HS Modem can be in either command mode or
WARNING
data mode. When the modem is idle, it is in command
The HS Modem family of products has been FCC
mode by default and will recognize commands. When
Part 68 approved as data/FAX modems. Utilization
data transmission is in progress, the HS modem is in
of the Voice/Tone Port requires further registration.
the data mode state and will not recognize commands.
The FCC requires that the entire system, including
To force the HS Modem to recognize commands, the
the HS Modem and the handset or DTMF
host must send an “escape sequence” to the HS
transceiver, adhere to Part 68 rules.
Modem forcing it out of data mode and into command
mode.
TIP
RJ-11
ANALOG VOICE
T1
RING
JACK
INJECTED SIGNALS
SPK
SPEAKER
HS MODEM
CONTROL
FAMILY
RXD
NOTE: SPEAKER CONTROL AND PHONE
CONTROL ARE ANCILLARY CIRCUITS
V.24
DCD
SHOWN ELSEWHERE IN THIS DATA SHEET.
EIA-232-E
DSR
INTERFACE
* SIGNAL GND MUST BE CONNECTED TO
RI
EARTH GROUND
OR
CTS
UART
TXD
DTR
Vcc
Vcc
3
8
+
1
22K
RI
2
-
LM393
4
RST
LM393
4.7K
EXTERNAL RESET
10K
4.7uF
5
+
7
6
-
+5V
.1uF
Isolated
10K
GND
Envelope
Ring Detect
Figure 4.
HS Modem Family Application Diagram.
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0003 Revision K6 (08/04)
Cermetek Microelectronics, Inc.
AT [Commands]<CR>.
Step 2. Initial Modem Training. The modem must be
Where: AT represents attention sequence. A and T
trained to the host DTE speed and parity (odd,
may be either upper or lower case but must be
even, mark, space or none). These activities
the same case.
[ Command ] represents
are briefly described below.
command strings.
HS Modem Reset. Upon applying power to the HS
Where: <CR> represents carriage return (ASCII 13 or
Modem, the HS Modem automatically generates an
HEX 0D)
internal reset pulse.
The user can also reset the
<LF> represents line feed (ASCII 10 or HEX
modem externally by applying a high-going reset pulse
0A)
to the RST pin for at least 10 msec after the +5V
power
supply
has
stabilized.
Delay
sending
The HS Modem will respond with one of the following
commands to the HS Mode for 2 seconds after reset