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Modem 3600
10-1
Chapter 10
Status Registers
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.
Information stored in 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
S-registers by the AT command set, but this action is transparent to the
user. The command indicates which memory bit(s) to alter to select an
option or to perform a function. The S-register values comprise the
configuration profile.
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 an S-register.
Note
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 a similar activity.
Some S-registers cannot be altered by the ATS command series. These are
called “read only” S-registers. In addition to the definitions in this chapter,
Appendix E contains a quick list of S-registers and indicates if they are
read only or read and write.
Figure 10-1 shows how the inputs to an S-register (S22 in this example)
are used to select a particular option. Bits 3 and 2 of S22 control speaker
options. Some communication software packages may use the AT
command set. For example purposes, bit values are arbitrary.