S-Registers

AT command settings are stored in the S-Registers. S-Register values can be changed either by entering an AT command or by entering the new value of the S-Register, preceded by AT, like this:

ATSn=v

where n is the number of the S-Register you want to change and v is the new value of that S-Register.

For example, follow the steps below if you want to change from manual answer (when you answer the call) to auto-answer (where the modem picks up the call after a certain number of rings), and have the call answered after three rings:

1. Check the table below to find the S-Register that controls answering. The registers are listed in numerical order. Note that you want to use S0.

2. Enter your communications software.

3. Enter Terminal mode.

4. Enter ATS0=3. The modem will now answer a call after three rings.

Register

Function

Range

Default
       

S0

Number of rings before the modem auto-answers a call. If set to 0, auto-answer is disabled and manual answer is in effect

0-255

0 rings
       

S1

Counts and logs the number of rings

0-255

0 rings
       

S2

Designates the ASCII character used to indicate an escape character (refer to an ASCII character conversion chart)

0-127

ASCII 43
       

S3

Designates the ASCII character used for carriage returns (refer to an ASCII character conversion chart)

0-127

ASCII 13
       

S4

Designates the ASCII character used for line feeds (refer to an ASCII character conversion chart)

0-127

ASCII 1
       

S5

Designates the ASCII character used for backspaces

0-127

ASCII 8
       

S6

Dial tone wait time; if AT command X is set to X2 or X4, the modem ignores this register and dials as soon as it detects a dial tone

2-255

2 seconds

       

S7

Carrier wait time

1-255

60 seconds
       

S8

Pause in dialing time (comma in dialing string)

0-255

2 seconds
       

S9

Carrier detect validation time (1/10 second)

1-255

6
       

S10

Delay time between lost carrier and hangup; if S1=255, the modem will not hang up when the carrier is lost; dropping DTR hangs up the modem (1/10 second)

1-255

7
       

S11

Duration of the touchtone dialing tone spacing

50-255

70 ms
       

S12

Guard time for the escape code (1/50 second)

0-255

50
       

S13

Bitmapped register. Selects the bit(s) you want on and sets S13 to the total of the values in the Value column. For example, ATS13.0=17 enables bit 0 (value 1) and bit 4 (value 16)

0-255

0
 

1 = Reset on DTR loss

    
 

2 = Reduced non-ARQ transmit buffer

    
 

4 = Set DEL=backspace

    
 

8 = Do DS0 on DTR

    
 

16 = Do DS0 on Reset

   
 

128 = Escape code hangup

    
       

S15

Bitmapped register.

0-255

0
 

1 = MNP/V.42 disabled in V.22

    
 

2 = MNP/V.42 disabled in V.22bis

    
 

4 = MNP/V.42 disabled V.32, V.34

   
 

8 = Disable MNP handshake

    
 

16 = Disable MNP level 4

    
 

32 = Disable MNP level 3

    
 

64 = Unusual MNP incompatibility

    
 

128 = Disable V.42

    
 

136 = Disable V.42 detection phase

    
       

S16

Bitmapped test register. 2 = Dial test

2

0
       

S18

Test timer for AT command &T; when AT&T=0 the timer is disabled.

0-255

0 sec
       

S19

Duration for inactivity timer; S19=0 disables the timer

0-255

0
       

S21

Sets error correction break length (1/100 second)

0-255

10
       

S22

Designates the ASCII character code for XON

0-127

ASCII 17
       

S23

Designates the ASCII character code for XOFF

0-127

ASCII 19
       

S25

DTR debounce time indicator (1/100 second)

0-255

5
       

S27

Bitmapped register.

-

0
 

1 = V.21 mode

    
 

2 = Disable TCM

    
 

4 = Disable V.32

    
 

8 = Disable 21Hz

    
 

16 = Enable V.23 fallback

    
 

32 = Disable V.32bis

    
 

128 = Software compatibility mode

    
       

S28

V.32 Handshake Time (1/10 second)

0-255

8
       

S29

V.21 Answer Mode Fallback Timer

0-255

20
       

S32

Connection bitmapped operations.

-

2
 

1 = V.8 call indicate enable

    
 

2 = Enable V.8 mode*

    
 

8 = Disable V.34 modulation

    
 

16 = Disable V.34+ modulation

   
 

32 = Disable x2 modulation*

    
 

64 = Disable V.90 modulation

   
 

* Be sure to enable 2.8 mode when disabling X2

    
       

S33

V.34 and V.34+ connection setup bitmapped control flags.

-

32

 

1 = Disable 24 symbol rate

    
 

2 = Disable 2743 symbol rate

    
 

4 = Disable 28 symbol rate

    
 

8 = Disable 3 symbol rate

    
 

16 = Disable 32 symbol rate

    
 

32 = Disable 3429 symbol rate

    
 

128 = Disable shaping

    
       

S34

V.34 and V.34+ connection setup bitmapped control flags

-

0
 

16 = Disable nonlinear coding

    
 

32 = Disable transmit level deviation

    
 

64 = Disable preemphasis

    
 

128 = Disable precoding

    
       

S38

Delay before forced hangup (optional)

0-255

0