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56K V.92 Data, Fax, and Voice Chipset
Programmer’s Guide Intel Confidential 101
7. S-REGISTERS
The MD566X chipsets provide direct access to the internal registers known as S-registers. The
DTE uses S-registers to set up and check modem configurations. The contents of these registers
can be changed using the ATSn=x command, where ‘n’ is the register number and ‘x’ is the value
to be stored. The contents of the S-registers can be read using the ATSn? command. Most S-
registers can be read from or written to; however, some S-registers (such as S14) are read-only.
Writing to a read-only register may cause the modem to act improperly (that is, even though the
contents of a read-only S-register may be changed using the ATSn=x command, changing the
contents of the S-register does not normally configure the entire modem).
Reserved S-registers are used by the modem and provide no valuable information to the DTE.
These registers have been removed from the following table. Reserved S-registers should never be
written to, as they cause the modem to lock up.
Table 7-1. S-Register Command Descriptions
Note: An asterisk (*) denotes the factory-default setting.
Command Default Description
S0 0
Number of Rings to Auto-Answer On
: Assigning S0 a value from 1 to 255 config-
ures the modem for auto-answer mode. The modem automatically goes off-hook
and initiates a data mode-answer mode handshake after detecting the specified
number of rings. This S-register is meant for data modem mode only and should be
set to “0” for fax and voice modes.
Range: 0–255 rings
n = 0 Auto-answer mode disabled
n = 1-255 Auto-answer mode enabled
NOTES:
1) If Caller ID is enabled (+VCID=n), then the modem only answers after the sec-
ond ring even if S0=1.
2) Setting n > 2 causes the modem to answer on the n
th
ring signal.
S1 0
Ring Count
: Reports the number of ring signals detected by the modem. This reg-
ister is cleared to zero if no new ring signals are detected within an 8-second time
interval.
Range: 0–255 rings
Default: 0 rings
S2 43
Escape Character
: S2 specifies an ASCII value for the Hayes or TIES escape char-
acter. The factory default is “+” or ASCII decimal 43. The escape character may
range between 0–127. Any value over 127 disables the escape sequence.
Range: 0–127
Default: 43 (“+”)