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2 ROM chips that have their data placed into them at the factory. They retain their
information when the power is switched off. You cannot make changes to information stored
in ROM chips. Information such as factory default settings for S Registers is stored in your
modem’s ROM chips.
3 Non-volatile memory retains data without requiring power. You can change the data in non-
volatile memory by using a special command (&Wn) to write the current settings to memory.
This memory can be used to provide a more permanent storage of changes you make to the
settings of your modem.
Any parameter stored in RAM will take precedence over any other stored in non-volatile
memory or ROM. Any parameter stored in non-volatile memory will take precedence over those
stored in ROM.
If you have not made any changes to your modem’s settings since it was unpacked after
purchase, the default parameters in ROM will control the modem.
If you have made changes and stored them as profiles in non-volatile memory — using the Write
Configuration (&Wn) command where n = profile 0,1,2 or 3— those settings that have been
changed in the active profile will take precedence over those in ROM, even after switching the
modem off and on.
Temporary changes — made during a communications session — to values using any A T
command, will be stored in RAM and will take precedence until you switch the modem off.
To use the current S Register settings with the Write Configuration command (&Wn):
• Type: AT&Wn <E>
(where n = the profile number you wish to use 0-3)
To return to the original factory default settings:
• Type: AT&F <E>
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Re-loading the factory default settings with AT&F will not save these default
settings to non-volatile memory.
To save factory defaults to non-volatile memory so they can be used again, after switching the
modem off and on, follow the &F command with the Write Configuration (&Wn) command.
To reset and store all settings to the factory default:
• Type: AT&F.