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| 型號(hào)： | CH1792 |
| 英文描述： | MODEM |
| 中文描述： | 調(diào)制解調(diào)器 |
| 文件頁(yè)數(shù)： | 2/16頁(yè) |
| 文件大小： | 1942K |
| 代理商： | CH1792 |
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2000 Cermetek Microelectronics, Inc.
Page 2
Document No. 607-0003 Revision G (05/00)
Telephone Line Interface or DAA.
High performance modems are extremely sensitive to DAA
(Data Access Arrangement) performance. The difference
between a good modem and a fair one is in the DAA
performance. The HS Modem family includes a unique low
distortion DAA designed for optimal performance over all
PSTN line conditions thereby achieving the most reliable and
best performance PSTN connections.
The HS Modem family is designed to meet North American
telephone standards as set by FCC Part 68 (USA) and CSA
CS-03 Part I (Canada). Among the more critical parameters,
the PSTN line interface is designed to meet 1500 VAC RMS
isolation and 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 specify these
levels of isolation.
Pins 1 and 2 function as both input and output connections to
the PSTN. To maximize field reliability in hostile
environments, for Canadian approval, for UL compliance, and
also optionally for FCC Part 15 compliance, these two pins
must be routed through an external network such as that
described in Figure 6A and in Cermetek Application Note #
126.
Each HS Modem product comes with FCC Part 68 approval
and is shipped from the factory with an FCC label indicating
registration number and ringer equivalent. This label should
be prominently displayed on the end product. With the
exception of the U.S., most countries (including Canada)
require submission of the final product or system containing
the HS Modem 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/consultant then
forwards the test results and applicable documents to the
regulatory agency. Contact Cermetek for a list of suggested
consultants.
Modulation/Demodulation/ Error Correcting and Data
Compression.
These functions are provided by an industry standard modem
chip set which has been adapted for use with the HS Modem
Family. The Modulation/Demodulation scheme supports the
industry modem standards listed below.
Bell 103
Bell 212A
CCITT V.22
CCITT V.22bis
CCITT V.32
CCITT V.32bis
CCITT V.34
CCITT V.34bis
CCITT V.90
The HS Modem supports V.42 LAMP, MNP 2-4, MNP 10
error correcting protocols. The CH1794 uses MNP5 data
compression techniques and the CH1798/9/CH2056 uses
V.42bis data compression, allowing data transmission rates
of up to a maximum of 57.6kbps/115.2kbps/230.4kbps,
respectively. These high DTE data rates are supported by
the HS Modem serial interface via its auto baud capability.
Note that the maximum speed attained is limited by the
maximum speed available from the DTE.
The
equalization and forward error correction.
resident
Modulator/Demodulator
supports
line
CONNECTING TO THE HOST UART
Since a modem communicates data serially and most host
products handle data in a parallel format, a UART is needed
to make parallel-to-serial and serial-to-parallel translations.
SUPPORTED FEATURES
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
proper logic level. See Table 3.
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 ohm 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 Atm 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 3 indicates one method of driving an
external 8 ohm speaker.
Zero Power Mode.
If an application calls for zero power during standby periods,
the power may be switched off using external circuitry and
then reapplied when the HS Modem’s RI pin becomes
active. The HS Modem can thus be powered down to zero.
Referring to Figure 2, the controller activates the relay
switch, supplying power (+5V) to the HS Modem. In this
configuration, the ring signal is used to “wake up” the HS
Modem when the HS Modem is in the power down state.
The pins of the HS Modem 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 HS Modem during power down.
Power Supply.
The HS Modem module is a complex set of sensitive
subsystems. During the course of normal operation, the HS
Modem 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 25 mV peak to peak. If
necessary, use dedicated power and ground planes. Failure
to provide such operating conditions could cause the HS
Modem to malfunction or to function erratically.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| CH1793 | MODEM |
| CH1793ET | Telecommunication IC |
| CH1793LT | Telecommunication IC |
| CH1798 | Telecommunication IC |
| CH1798ET | MODEM |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CH1793 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MODEM |
| CH1793ET | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
| CH1793LT | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Telecommunication IC |
| CH1794 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:HIGH SPEED Modem and FAX FAMILY |
| CH1794A | 制造商:Cermetek Microelectronics 功能描述:Modem Chip Single 57.6Kbps 22-Pin |
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