Z02205
Modem Controller
ZiLOG
10 PS001000-MOD0599
AT COMMAND SET
Command lines are typed to the modem from the terminal
when the modem is in the Idle or Command state. The mo-
dem does not execute any commands from a command line
until the command line is ended by the end of line character
<
CR>. A command line is a string of characters starting with
A and T characters and ending with a special end-of-line
character, <
CR>. Characters typed before the AT are ig-
nored. Command lines contain no more than 40 characters
after the
AT (not counting spaces). The modem does not ex-
ecute any 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
are entered.
A partial command line can be aborted by typing a Ctrl-X
character. The modem returns an OK result code and ig-
nores 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 cause any subsequent commands in the com-
mand line to be ignored.
Command Line Execution
The characters in a command line execute one at a time. Any
unexpected characters, except control characters, stop com-
mand line execution and return an
ERROR result code. Un-
expected characters include numbers outside 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 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 ter-
minal.
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 is 2 and ATS01
is 2 both set S-register S1 to 2.
All numeric arguments, including S-register numbers, are
decimal.
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 default
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 Table 2 are denoted by bold.
.
