RFL Electronics RFL 9660, Инструкция по эксплуатации, Страница: 155 / 312

RFL 9660 RFL Electronics Inc.
April 24, 2007 13-2 (973) 334-3100
13.2 “AT” COMMANDS
13.2.1 “AT” Command Format
A command line is a string of characters sent from a DTE to the modem (DCE) while the modem is in a
command state. A command line has a prefix, a body, and a terminator. Each command line (with the
exception of the A/command) must begin with the character sequence AT and must be terminated by a carriage
return. Commands entered in upper case or lower case are accepted, but both the A and T must be of the same
case, i.e., “AT” = ASCII 065, 084 or “at” = ASCII 097, 116. The body is a string of commands restricted to
printable ASCII characters (032-126). Space characters (ASCII 032) and control characters other than CR
(ASCII 013) and BS (ASCII 010) in the command string are ignored. The default terminator is the ASCII <CR>
character. Characters that precede the AT prefix are ignored. The command line interpretation begins upon
receipt of the carriage return character.
Characters within the command line are parsed as commands with associated parameter values. The basic
commands consist of single ASCII characters, or single characters preceded by a prefix character (e.g., “&”),
followed by a decimal parameter. Missing decimal parameters are evaluated as 0.
The modem supports the editing of command lines by recognizing a backspace character. When modem echo
is enabled, the modem responds to receipt of a backspace or delete by echoing a backspace character, a
space character, and another backspace. The hex value to be used for the backspace character is
programmable through register S5. Values equal to 0 or greater than 127, or the value which corresponds to the
carriage return character, cannot be used for the backspace character. This editing is not applicable to the AT
header of a command. A command line may be aborted at any time by entering <cntrl-x> (18h).
The AT sequence may be followed by any number of commands in sequence, except for commands such as Z,
D, or A. Commands following commands Z, D, or A on the same command line will be ignored. The maximum
number of characters on any command line is 39 (including “A” and “I”). If a syntax error is found anywhere in a
command line command, the remainder of the line will be ignored and the ERROR result code will be returned.
Most commands entered with parameters out of range will not be accepted and the ERROR response will be
returned to the DTE.
Commands will only be accepted by the modem once the previous command has been fully executed, which is
normally indicated by the return of an appropriate result code. Execution of commands D and A, either as a
result of a direct command or a re-execute command, will be aborted if another character is entered before
completion of the handshake.
13.2.2 Escape Code Sequence
When the modem has established a connection and has entered on-line data mode, it is possible to break into a
data transmission in order to issue further commands to the modem in an on-line command mode. This is
achieved by the 9660 sending the following sequence to the modem:
+++AT [CR].
The first three characters of the sequence is determined by the value of register S2. The default value of
register F2 is 43 (+). The modem can be returned to the data mode by entering ATO [CR].
To disable the local escape sequence, enter the command ATS2=128.
The remote modem can also break into the data transmission to issue commands to the 9660 modem. This is
achieved by the remote modem sending the following sequence:
%%%ATMTSMODEM [CR].
The first three characters of the sequence are specified by register S9. The default value of register S9 is
37 (%). The modem can be returned to the data modem by entering ATO [CR]. To disable the remote escape
code sequence, enter the command ATS9=0.