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536EX Chipset Developer’s Manual 85
Intel Confidential
S-Registers
S-Registers 7
The 536EX 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 26. S-Register Command Descriptions
Command Default Description
S0 0
Number of Rings to Auto-Answer On: Assigning S0 a value from 1 to 255 configures 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
0 Auto-answer mode disabled
1–255 Auto-answer mode enabled
NOTES:
• If Caller ID is enabled (+VCID=m), then the modem only answers after the second ring
even if S0=1.
• 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 register 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 character. 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 (‘+’)
S3 13
Carriage Return Character: S3 specifies the AT command string terminator and modem
response code terminator. The factory default is a <CR> or carriage return (ASCII decimal 13).
Range: 0–127
Default: 13 (carriage return)
S4 10
Line Feed Character: S4 specifies the line feed character, which is used for verbose (text)
modem result codes.
Range: 0–127
Default: 10 (line feed)
NOTE: An asterisk (*) denotes the factory-default setting.