Comtrol AT Commands - Manual (Page 23)

AT Commands for CX81801/CX06833/CX81300/CX06827 Modems Reference Manual
102184B Conexant 2-9
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:
1. The characters transmitted for the header are determined by the V command.
2. The trailer consists of two characters, being the character having the ordinal value of
parameter S3 followed by the character having the ordinal value of parameter S4.
3. Information text usually consists of a single line; information text returned in
response to some commands may contain multiple lines, and the text may therefore
include CR, LF, and other formatting characters to improve readability.
Result Code Parts. Result codes consist of three parts: a header, the result text, and a
trailer.
1. The characters transmitted for the header and trailer are determined by the V
command setting.
2. The result text may be transmitted as a number or as a string, also depending on a the
V command setting.