HIGH SPEED Modem and FAX FAMILY
CH2056
CH1799
CH1798
CH1794
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V.90 / 56,000bps
V.34bis / 33,600bps
V.34 / 28,800bps
V.32bis / 14,400bps
INTRODUCTION
FEATURES
The CH2056, CH1799, CH1798 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 56,000bps. By using built in compression
algorithms the operating speed can be expanded to the
maximum DTE rate of 57.6kps for the CH1794, 115.2Kbps
for the CH1798/CH1799 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
supports Send and Receive Fax. The CH1799LL operates
exclusively on non-voltage bearing leased line.
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Supports V.90, V.34bis, V.34, V.32bis, V.32, V.22bis,
V.22A/B, V.23, V.21, Bell 212A and 103
CH2056 supports V.80 Synchronous operation
Error correcting: V.42 LAMP, MNP 2-4 and MNP 10
Data Compression: V.42bis and MNP 5
MNP10 Data throughput enhancement for cellular
operation
DTE serial interface with speeds up to 230.4kbps
(CH2056), 115.2kbps (CH1799/CH1798) or 57.6kbps
(CH1794)
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Automatic baud rate adaptability utilizing speed sensing,
flow control and data buffers
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Send & Receive Fax Class 1, Group 3 supported
Serial V.24, 5 volt interface
NVRAM directory and stored profiles
AT Command structure, with extensions
Built-in DAA with 1500 VAC RMS isolation 2122V peak
surge protection
UL 1950 and CSA C22.2 950 Recognized
Leased Line version available CH1799LL
FCC part 68 Approved/DOT CSA CS-03 Part
Approveable
+5 Volt operation with zero power option
Small size: 1.35” x 1.38” x 0.61” (nominal)
Pin compatible with low speed/low cost CH1786
The HS Modem family is pin compatible with Cermetek’s low
cost CH1786 V.22bis, 2400bps modem family. Each module
in the HS Modem family is a self-contained modem and is
FCC Part 68 approved and Canadian DOT approveable.
These ultra small modules are designed for PCB through-
hole mounting and are 1.35” x 1.38” x 0.58” in size. The HS
Modem family requires only 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-
11C Jack for the PSTN line connection. The HS Modem can
be controlled with industry standard AT commands and is
compatible with available industry communication software.
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Figure 1. Function Block Diagram of HS Modem Family.
DESCRIPTION OF FUNCTIONAL BLOCKS AND
DISCUSSION OF BASIC OPERATIONS
Figure 1 contains a functional block drawing of the HS
Modem family of products. Each HS Modem product
consists of a serial interface buffer, modulator/demodulator,
modem controller with error correction and data compression,
non-volatile RAM and a DAA.
Serial Host Interface Buffer.
The HS Modem utilizes a serial V.24 EIA 232-E 5V interface
to control the modem. The HS Modem products can
communicate over the serial interface with the Data Terminal
Equipment (DTE) at a fixed speed regardless of the carrier
line modulation speed (DCE) of the PSTN modem
connection. This eliminates the need to have the DTE step
up or step down in speed based on the incoming or out-going
PSTN communication data rate. Hence, the DTE can train
the CH2056, to say 56kbps, and talk to a slower incoming
data connection at say, 2400bps without changing host
speed. Conversely, the host DTE trained at 14.4kbps can
also communicate with the modems at higher speeds, say
upon reset or power up. The ATZn command immediately
recalls and activates a stored configuration. See Tables 7A
and 7B for storable S-Registers and Commands.
28.8kbps.
This is accomplished by invoking internal
automatic data flow control. The HS Modem family has a
resident buffer to allow for this auto baud operation.
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 ATDS=n command will cause the modem to dial
one of the four stored telephone numbers. The NVRAM
storage location for the four telephone numbers is selected
by an n of 0, 1, 2, or 3.
Non-Volatile RAM (NVRAM).
NVRAM can store two user-customized configurations. The
AT&Wn command will store the active modem configuration
in one of two NVRAM locations as selected by an n of 0 or 1.
The AT&Yn command selects one of the stored modem
configurations to be automatically recalled and made active
ã 2000 Cermetek Microelectronics, Inc.
Page 1
Documt No. 607-0003 Revision G (05/00)
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