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Chapter 6 – S-Registers
Multi-Tech Systems, Inc. AT Commands Reference Guide (S000273G) 44
S-Reg Unit Range Default Description
S29 10 ms 0–255 70 On Hook Time: Sets the length of time that the modem goes on-hook when it
encounters a flash dial modifier (!) in the dialing string.
S30 10 seconds 0, 1–255 0 Disonnect Inactivity Timer: Sets the length of time that the modem waits before
disconnecting when no data is sent or received. A value of zero disables the timer.
Applies to asynchronous operation only.
S36 decimal 0–7 7 LAPM Failure Control: Specifies the fallback action to take in the event of an
LAPM negotiation failure. These fallback options are initiated immediately upon
connection if S48 is set to 128. If an invalid number is entered, S36 acts as if the
default value has been entered. (See S48.)
0 Modem disconnects.
1 Modem stays online and a direct mode connection is established.
3 Modem stays on-line; normal mode connection established.
4 MNP connection is attempted. If it fails, modem disconnects.
5 MNP connection is attempted. If it fails, a direct mode connection is established.
7 An MNP connection is attempted and if it fails, a normal modem connection is
established.
S38 seconds 0–254, 20 Delay Before Forced Hang Up: Sets the delay between the modem’s receipt of
255 the H command to disconnect (or high-to-low transition of DTR if the modem is
programmed to follow the signal) and the disconnect operation. Applies only to
error-correction connections. This register can be used to ensure that data in the
modem buffer is sent before the modem disconnects. If S38 is set between 0 and
254, the modem waits for the remote modem to acknowledge all data in the buffer
before disconnecting. IfS38 is set to 255, the modem does not time out and
continues to attempt to deliver data in the buffer until the connection is lost or the
data is delivered.
S46 decimal 136, 138 Data Compression Control: Enables/disables data compression:
138 136 Error correction without compression.138 Error correction with compression.
S48 decimal 0, 7, 7 V.42 Negotiation Control: Enables or disables LAPM negotiation.
128 An invalid value is treated as a 128 value.
0 Disables negotiation and proceeds with LAPM.
7 Enables negotiation.
128 Disables negotiation. Proceeds at once with the fallback action specified in
S36. Can be used to force MNP.
S86 decimal 0, 3–23 n/a Call Failure Reason Code: When the modem issues a NO CARRIER result code,
a value is written to this register to help determine the reason for the failed
connection. S86 records the first event that contributes to a NO CARRIER
message. Use the S86? command to read the value.
0 Normal disconnect; no error occurred.
3 Call Waiting caused disconnect.
4 Physical loss of carrier.
5 No error correction at the other end.
6 No response to feature negotiation.
7 This modem is async-only, the other sync-only.
8 No framing technique in common.
9 No protocol in common.
10 Bad response to feature negotiation.
11 No sync information from remote modem.
12 Normal disconnect initiated by remote modem.
13 Remote modem doesn’t respond after 10 retransmissions of the message.
14 Protocol violation.
15 DTR lost.
16 Received GSTN clear down.
17 Inactivity timeout.
18 Speed not supported.
19 Long space disconnect.
20 Key abort disconnect.
21 Clears previous disconnect reason.
22 No connection established.
23 Disconnect after three retrains.
24 Call Waiting tone detected.
25 Extension pickup detected.
26 Remote hang up detected.