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CH224ATF

Complete 2400 bps Modem Module

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

Data modes perform complete handshake and

data rate negotiations. All tone and pattern

detection required by the applicable CCITT or

Bell standard are supported.

Fax modes support Group 3 fax requirements.

Fax data and fax control (V.21 300 bps)

performed by the modem is controlled and

monitored through the fax EIA-578 Class 1

insertion/deletion,

and

CRC

generation/checking is provided.

Both transmit and receive fax data is buffered

within the modem. Data transfer to and from

the DTE is flow controlled by XON/XOFF.

Configurations and Rates

The supported modem configurations and

signaling rates are listed in Table 1. In data

modes with serial interface selected, DTE rate

offsets of +1%, -2.5% are accommodated by

adding/deleting stop bits are required. In fax

modes, the DTE rate is 19200 bps.

Operation

Modem operation is controlled by AT

commands (Table 2), fax service class 1

commands (Table 3), and supporting S registers

(Table 4). Result codes and messages are

listed in Table 5.

Data Modes: Data rate selection is determined

by the speed of the originating and answering

modems:

Originate Modem

Answer Rate

(bps)

Connect Speed Based on

Modem Rate (bps)

300 1200 2400

300

1200

2400

300

1200

1200

300 300

1200 1200

1200 2400

CH224ATF Complete 2400 bps Modem Module

Fax Modes: Fax modes are negotiated as

defined in T.30 and are implemented by AT+F

commands. The AT+FCLASS=1 command

causes entry into the fax mode from the data

mode. Most other fax class 1 commands,

which start with the AT+F prefix, are valid only

in the fax mode.All data commands are valid

in the fax mode except A/, On & Tn, and the

escape sequence (+++). The AT+FCLASS=0

command terminates the fax mode and

causes entry into the data mode.

AT Command Format

Each command line must start with the AT

prefix and be terminated with a carriage return

(CR). Several commands may be included on

one command line. A command line may

contain up to 40 characters excluding the AT

prefix and the terminating CR. A separator is

not required between data commands. A

semicolon (;) separator is required between

fax commands.

AT commands are composed of 10-bit ASCII

encoded asynchronous characters. The

character format in data mode is 8 data bits

with no parity, or 7 data bits with even, odd, or

no (two stop bits) parity, at a data rate of

19200, 2400, 1200, or 300 bps. The

character format in fax mode is 8 data bits

with no parity at 19200 bps.

Data Modulation

The data modulation conforms to V.29, V.27

ter, V.22 bis, V.22, V.21, Bell212A, or Bell

103, depending on the selected configuration.

Transmitter and receiver spectrum shaping is

provided in accordance with the applicable

standard.

Equalization

Automatic adaptive qualization as well as

fixed compromised equalization is provided to

compensate for line distortions and to

minimize the effects of the intersymbol

interference.

Scrambler/Descrambler

The modem incorporates a self-synchronizing

scrambler/descrambler satisfying the

applicable CCITT or Bell requirements.

2001 Cermetek Microelectronics, Inc.

Page 2

Document No. 607-0005 Revision B1 (05/02)

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