Telenetics 56 - Manual (Page 41)

AT Commands
Page 33
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.
Handling of Invalid Numbers and S-Parameter Values
The modem reacts to undefined numbers and S-parameter values in one of three ways:
™ Issue the ERROR result code, and leave the previous value of the parameter
unchanged;
™ Issue the OK result code, and leave the previous value of the parameter unchanged;
or,
™ 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.
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.