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4 AT Commands, S-Registers, and Result Codes
49
S-Registers
Certain modem values, or parameters, are stored in memory locations called S-
registers. Use the S command to read or alter the contents of S-registers (see previ-
ous section).
Register Unit Range Default Description
S0 1 ring 0, 1–255 1 Sets the number of rings before the modem
answers. ATS0=0 disables autoanswer
completely.
S1 1 ring 0–255 0 Counts the rings that have occurred.
S2 decimal 0–127 43 (+) Sets ASCII code for the escape sequence
128–255 character. Values greater than 127 disable
escape.
S3 decimal 0–127 13 (^M) Sets the ASCII code for the carriage return
character.
S4 decimal 0–127 10 (^J) Sets the ASCII code for the line feed
character.
S5 decimal 0–32 8 (^H) Sets the ASCII code for the backspace
33–127 character. Values greater than 32 disable
backspace.
S6 seconds 2–255 2 Sets the time the modem waits after it goes
off-hook before it begins to dial the phone
number.
S7 seconds 1–255 50 Sets the time the modem waits for a carrier
signal before aborting a call. Also sets the
wait for silence time for the @ dial modifier,
and the time the modem waits for the dial
tone after encountering W in the dial string.
S8 seconds 0–255 2 Sets the length of the pause caused by a
comma character in a dialing command.
S9 100 ms 1–255 6 Sets the time, in tenths of a second, that the
carrier must be present before the modem
considers it valid.
S10 100 ms 1–255 14 Sets how long a carrier signal must be lost
before the modem disconnects.
S11 1 ms 50–255 95 Sets spacing and duration of dialing tones.
S12 20 ms 0–255 50 Defines the maximum period, in fiftieths of
second, allowed between receipt of the last
character of the three escape character
sequence from the computer and the send-
ing of the OK result code to the computer.
(Escape code guard time).