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S-REGISTERS
Most modem configuration information is stored in a part of memory
called status (S) registers. During operation this information is used to
determine modem functions.
The information stored in the S-registers can be changed by the AT or
V.25 command sets and by pushbuttons in response to the LCD prompt.
These are the preferred methods. Some software programs also access
the S-registers via the AT command set, but this action is transparent to
the user. The command indicates which memory bit(s) to alter to select
a particular option or to perform a certain function. The S-register
values comprise the configuration profile.
Caution
The purpose of this tutorial is to show the versatility of
option selection and register function. It is strongly recom-
mended that the preferred methods of option selection be
used. This tutorial uses S22 as the example register.
Certain modems may use S22 differently or may not have an
S22.
Generally the user should not directly alter S-register values. However,
the user has the option of entering S-registers via ATS commands and
directly altering the register value. This is called "writing" to the S-
register. Writing to an S-register is not a preferred method and should
only be used by programmers who need to manipulate S-registers so
they can interact with a software program under development or some
other similar action.
Certain S-registers cannot be altered by the ATS command series.
These are called "read only" S-registers. Appendix E contains a listing
of S-registers and indicates if they are read only or read and write.
Status Registers
V.3400
Chapter 10
10-1
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