INTEGRATED CIRCUITS DIVISION
CPC2400E
www.ixysic.com
7
R03
Command lines are typed to the modem from the
terminal when the modem is in the Idle or Command
state. The modem does not execute any of the
commands in a command line until after the command
line is ended by the end of line character <CR>. A
command line is a string of char-acters starting with
the A and T characters and ending with a special
end of line character, <CR>. Characters typed before
the AT are ignored. Command lines contain at most
40 characters after the AT, not counting spaces. The
modem does not execute any of the commands in a
command line that is too long.
To Echo command line characters, use the E1
command.
Typing mistakes can be aborted by using a special
Back-Space character, <BS>, after the initial A and T
characters have been entered.
A partial command line can be aborted by typing a
Ctrl-X character. The modem returns an OK result
code and ignores the partial AT command line.
Command lines may contain several commands
one after another. The Answer (A), Dial (D), and Go
On-Line (O) commands usually cause any following
commands in the command line to be ignored.
Command Line Execution
The characters in a command line are executed one
at a time. Any unexpected characters, except control
characters, stop command line execution and return
an ERROR result code. Unexpected characters
include numbers out-side the range of values
accepted by the command. All control characters
in a command line except Ctrl-X and the special
characters such as <CR> and <BS> are ignored.
The numerical argument of a command is assumed
to be 0 if it was not provided. For example, the
commands ATH<CR> and ATH0<CR> both hang up
the telephone line.
When the modem has executed a command line the
result code of the last command executed is returned
to the terminal. If the value to be written to a modem
S-register is outside the range of values accepted
by the S-register then its value is set to the nearest
allowed value.
Leading zeros in numeric arguments, including
S-register numbers, are ignored. For example,
ATS1=2 and ATS01=2 both set S-register S1 to 2.
All numeric arguments, including S-register numbers,
are decimal (base 10).
AT Command Prefix
Each modem command line begins with the letters
A and T. The modem uses these characters to
determine the data rate and parity of data from the
terminal.
A/Repeat Last Command
To repeat the commands in the last command line
type the letters A and / instead of A and T.
<CR>End Of Line Character
This character is typed to end a command line. The
value of the <CR> character is stored in S-register S3.
The de-fault is 13, the ASCII carriage return character.
When the <CR> character is entered, the modem
executes the commands in the command line.
Note: default values in the AT Command Tables are
denoted by bold face type.