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Chapter 5 – AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 75
S-Registers
Certain modem values, or parameters, are stored in memory locations called S-registers. Use the S command to
read or to alter the contents of S-registers (see previous section). * Register value may be stored on one of two user
profiles with the command &W.
Register Unit
Range Default Description
S0 1 ring 0–255 0 Number of Rings to Auto-Answer: Sets the number of rings until
the modem answers. ATS0=0 disables autoanswer completely. *
S1 1 ring 0–255 0 Ring Counter: Counts the rings that have occurred. S1 is cleared if
no rings occur over eight-second intervals.
S2 decimal 0–255 43 (+) Escape Character: Holds the decimal value of the ASCII character
used as the escape character. The default value corresponds to an
ASCII ‘+’. A value over 127 disables the escape process; e.g., no
escape character will be recognized.*
S3 decimal 0–127 13 (^M) Carriage Return Character: Sets the command line and result code
terminator character. Pertains to asynchronous operation only.
S4 decimal 0–127 10 (^J) Line Feed Character: Sets the character recognized as a line feed.
Pertains to asynchronous operation only. The Line Feed control
character is output after the Carriage Return Control character if
verbose result codes are used.
S5 decimal 0–255 8 (^H) Backspace Character : Sets the character recognized as a
backspace. Pertains to asynchronous operation only. The modem will
not recognize the Backspace character if it is set to a value that is
greater than 32 ASCII. This character can be used to edit a command
line. When the echo command is enabled, the modem echoes back to
the local DTE the Backspace character, an ASCII space character
and a second Backspace character; this means a total of three
characters are transmitted each time the modem processes the
Backspace character.
S6 seconds 2–255 2 Wait Time Before Blind Dialing or for Dial Tone: 1. Sets the length
of time, in seconds, that the modem will wait before starting to dial
after going off-hook when blind dialing. This operation, however, may
be affected by some ATX options according to country restrictions.
The “Wait for Dial Tone” call progress feature (W dial modifier in the
dial string) will override the value in register S6. (When configured for
US).
2. Sets the length of time, in seconds, that the modem will wait for
dial tone when encountering a “W” dial modifier before returning NO
DIAL TONE result code. (W class). Default is country-dependent. The
modem always pauses for a minimum of 2 seconds, even if the value
of S6 is less than 2 seconds. *
S7 seconds 1–255* 50 Wait Time for Carrier, Silence, or Dial Tone:
1. Sets the length of time, in seconds, that the modem will wait for
carrier before hanging up. The timer is started when the modem
finishes dialing (originate), or 2 seconds after going off-hook (answer).
In originate mode, the timer is reset upon detection of answer tone if
allowed by country restrictions.
2. Sets the length of time, in seconds, that modem will wait for silence
when encountering the @ dial modifier before continuing with the next
dial string parameter.
3. Sets the length of time, in seconds, that the modem will wait for dial
tone when encountering a “W” dial modifier before continuing with the
next dial string parameter. (US model.)
The default is country dependent. *
S8 seconds 2–255 2 Pause Time for Dial Delay: Sets the time, in seconds, that the
modem must pause when the “,” dial modifier is encountered in the
dial string. *