Black Box 3600 MODEM manual Chapter Status Registers

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 theAT command set. For example purposes, bit values are arbitrary.

Modem 3600 10-1