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CH1782A

Family of Ultra Small Modem Modules V.22bis-2400bps

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

These activities are briefly described below.

Reset. Upon applying power to the CH1782A, the

CH1782A automatically generates an internal reset

pulse. The user may also reset the modem externally

by applying a high-going reset pulse to the RST pin

for at least 10ms after the +5V power supply has

stabilized. Delay sending commands to CH1782A for

200ms after reset has been initiated to allow the

CH1782A time to properly reconfigure.

Training the Modem. Each modem must be trained

to match its host’s speed and parity so that it is able

to recognize serial asynchronous commands sent to it

by the host’s is UART. The host must retrain the

modem each time a reset pulse is applied on RST or

after a RESET serial command has been issued.

CH1782A Family of Ultra Small Modem Modules V.22bis-2400bps

[Commands] represents command strings.

<CR> represents carriage return (ASCII 13

or HEX 0D).

When entering commands to the modem, the

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

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

edited. Multiple commands may be placed in the

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 CH1782A

to configure itself to not echo characters when in

command mode E0 and then put itself in answer

mode A.

Enter: ATE0A<CR>

Result: OK

Modem Training Command Sequence. The

CH1782A is trained by sending it the following

sequence:

Enter: AT<CR>

Result: OK

Where: A and T may be either upper or lower case

but must be the same case.

<CR> represents carriage return

The AT sequence is referred to as an attention

sequence. The CH1782A will respond with one of the

following status messages, depending on whether it

is optioned for Terse (abbreviated) or Verbose

(English) status messages.

Result: 0<CR> (Terse)

or

Result: <CR><LF>OK<CR><LF> (Verbose)

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

HEX 0D).

<LF> represents line feed (ASCII 10 or HEX

0A).

After responding with an OK, the CH1782A is in idle

mode and is ready to accept additional commands.

An alternate attention sequence A/ may be sent

which behaves much like the AT sequence except

that it causes the previously entered command

specified with an AT prefix to be executed. When

given, both the AT and A/ must be in upper case

ASCII. No carriage return is needed for the A/

command.

THE COMMAND FORMAT

Typical commands consist of three elements: the

attention sequence, the commands themselves, and

a terminating carriage return.

AT[commands]<CR>.

Where: AT represents attention sequence.

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 Table 5.

AT Command Data Rate. With the serial interface,

the rate is speed sensed for parity and format.

THE STATUS MESSAGES

The CH1782A responds with a status message after

each command is executed. This status message

may either be a single digit followed by a carriage

return or a carriage return and line feed with a

message in English, followed by a carriage return and

line feed.

n command. Where n=0, 1, 2, 3, 4 establishes the

result codes allowed by the user.

X0: Result Codes 0, 1, 2, 3, 4 allowed

X1: Result Codes 0, 1, 2, 3, 4, 5, 10 allowed

X2: Result Codes 0,1, 2, 3, 4, 5, 6, 10 allowed

X3: Result Codes 0, 1, 2, 3, 4, 5, 7, 10 allowed

X4: Result Codes 0, 1, 2, 3, 4, 5, 6, 7, 10 allowed.

NOTE

The CH1782A is factory set to X4, which allows all

result codes.

MODEM STATES

The CH1782A can be in either command mode or

data mode. When the modem is idle, it is in

command mode by default and will recognize

commands. When data transmission is in progress,

the CH1782A is in the data mode state and will not

recognize commands. To force the CH1782A to

recognize commands, the host must send an escape

sequence to the CH1782A forcing it out of data mode

and into command mode.

2002 Cermetek Microelectronics, Inc.

Page 4

Document No. 607-0009 Revision C (01/03)

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