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CH1794

HIGH SPEED Modem and FAX FAMILY

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

AT [Commands]<CR>.

Where: AT represents attention sequence. A and T

may be either upper or lower case but must be

the same case. [Command] represents

command strings.

Where: <CR> represents carriage return (ASCII 13 or

HEX 0D)

<LF> represents line feed (ASCII 10 or HEX

0A)

The HS Modem will respond with one of the following

status messages depending on whether it is optioned

for abbreviated (terse) or English (verbose) status

messages.

Result: 0 <CR> (Terse)

or

Result: <CR><LF>

OK

<CR><LF> (Verbose)

After accepting the AT<CR> command the HS modem

is in idle mode and is ready to accept additional

commands.

An alternate attention sequence A/ may be issued

which behaves much like the AT sequence except that

it causes the last entered command specified with an

AT prefix to be executed. When given, it must be in

upper case ASCII. No carriage return is needed for

this command.

High Speed Modem and FAX Family

Step 2. Initial Modem Training. The modem must be

trained to the host DTE speed and parity (odd,

even, mark, space or none). These activities

are briefly described below.

HS Modem Reset. Upon applying power to the HS

Modem, the HS Modem automatically generates an

internal reset pulse. The user can also reset the

modem externally by applying a high-going reset pulse

to the RST pin for at least 10 msec after the +5V

power supply has stabilized. Delay sending

commands to the HS Mode for 2 seconds after reset

has been initiated to allow the HS Modem time to

properly reconfigure.

On power up, or when reset is initiated either by the

ATZ<CR> command or by the RST pin, the modem

will reconfigure to its default state with the line carrier

modulation speed set to:

1. 14.4kbps for the CH1794

2. 33.6kbps for the CH1799

3. 57.6kbps for the CH2056

If desired, any speed, error correction, or data

compression method available on the HS Modem can

be locked in, using the ATNn and/or AT+MS

commands.

Training the Modem. Each modem must be trained

to match the host DTE speed and parity so that it is

able to recognize serial asynchronous commands sent

to it by the DTE.

When entering commands to the modem, the

backspace character-control-H (ASCII 8 or HEX 08)

can be used to edit mistakes. AT and A/ may not be

edited however. Multiple commands may be placed

on a 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 HS Modem

to configure itself to not echo characters when in

command mode (E0) and then puts itself in answer

mode (A).

Enter: ATE0A<CR>

Result: OK<CR><LF>

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 Tables 6A and 6B.

INITIALIZING THE MODEM

Before commands may be sent to the HS Modem, the

modem must be initialized. This is a two step process:

Step 1. Modem Reset. This is accomplished by

applying a hardware-reset pulse to pin RST or

by switching the power off then back on.

The DTE must retrain the modem each time a reset

pulse is applied on RST or after a RESET serial

command has been issued.

STATUS MESSAGES AND RESULTS CODES

A result code is issued by the HS Modem to the DTE

for all commands executed by the HS Modem except

dialing commands. Further, various activities on the

PSTN are also signaled to the DTE by the HS Modem.

All result codes have either a terse, short form version

(which is identified by a number followed by a <CR>)

or a verbose long form English-like message version

(which is preceded and terminated with a <CR> and

<LF>).

The user may suppress certain subsets of the non-

extended result codes. This is accomplished by

selecting subsets of the result code set using the

ATXn command, where n=0, 1, 2 or 3. Optionally, the

user may specify an extended set of results codes

(codes above 35) by setting Register S95. See the

detailed description of results codes in Table 5A, 5B

and 5C.

All AT commands, other than dialing commands, will

be responded to with either an OK (short form result

2003 Cermetek Microelectronics, Inc.

Page 6

Document No. 607-0003 Revision K3 (09/03)

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