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commands in the command line in the order received from the DTE. Should execution of
a command result in an error, or a character be not recognized as a valid command,
execution is terminated, the remainder of the command line is ignored, and the ERROR
result code is issued.
Otherwise, if all commands execute correctly, only the result code associated with the
last command is issued; result codes for preceding commands are suppressed. If no
commands appear in the command line, the OK result code is issued.
2.6.1 Aborting Commands
Some action commands that require time to execute may be aborted while in progress;
these are explicitly noted in the description of the command. Aborting of commands is
accomplished by the transmission from the DTE to the modem of any character. A single
character is sufficient to abort the command in progress; however, characters
transmitted during the first 125 milliseconds after transmission of the termination
character are ignored (to allow for the DTE to append additional
control characters such as line feed after the command line termination character). To
ensure that the aborting character is recognized by the modem, it should be sent at the
same rate as the preceding command line; the modem may ignore characters sent at
other rates. When such an aborting event is recognized by the modem, the modem
terminates the command in progress and returns an appropriate result code to the DTE,
as specified for the particular command.
2.6.2 Handling of Invalid Numbers and S-Parameter Values
The modem reacts to undefined numbers and S-parameter values in one of three ways:
1. Issue the ERROR result code, and leave the previous value of the parameter
unchanged;
2. Issue the OK result code, and leave the previous value of the parameter unchanged;
or,
3. Issue the OK result code, and set the parameter value to the valid value nearest to
that specified in the command line. The description of each command specifies which of
these three techniques is used to handle invalid parameter values for that command or
parameter.
2.7 Modem Responses
While in command state and online command state, the modem will issue responses
using the same rate, word length, and parity as the most recently received DTE
command line. In the event that no DTE command has yet been received, rate, word
length, and parity used will depend on the capabilities of the modem. When the modem
transitions from the command state or online command state to the online data state, the
result code CONNECT should be issued at the bit rate and parity used during the
command state. When the modem transitions from the online data state to the command
state or online command state, the result codes should be issued at the bit rate used
during the online data state. Thereafter, any unsolicited result codes should use the bit
rate and parity of the last command line issued by the DTE to the modem. The
characters of a response will be contiguous, with no more than 100 milliseconds of mark
idle issued between characters in addition to stop elements
.
2.7.1 Responses
There are two types of responses that may be issued by the modem: information text
and result codes.
Information Text. Information text responses consist of three parts: a header, information
text, and a trailer:
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