CH1786NH 데이터 시트보기 (PDF) - Cermetek Microelectronics

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CH1786NH

CH1786 Family of Ultra Small 2400bps Modems

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

Reset. Upon applying power to the CH1786, the

CH1786 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 CH1786 for

200ms after reset has been initiated to allow the

CH1786 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.

Modem Training Command Sequence. The

CH1786 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 CH1786 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 CH1786 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.

[Commands] represents command strings.

CH1786 Family of Ultra Small 2400bps Modems

<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 CH1786

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

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 CH1786 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.

The basic status code subsets are enabled with the

Xn 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 CH1786 is factory set to X4, which allows all

result codes.

MODEM STATES

The CH1786 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 CH1786 is

in the data mode state and will not recognize

commands. To force the CH1786 to recognize

commands, the host must send an escape sequence

to the CH1786 forcing it out of data mode and into

command mode.

2003 Cermetek Microelectronics, Inc.

Page 5

Document No. 607-0004 Revision L1 (06/03)

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