22 Basic Modem Operation
Saving Settings and User Profiles
There are some cases where you may wish to save the settings you
have made as the default settings that are recalled when your
modem is powered up. The AT&WZ command selects the current
settings as the power-on profile.
There are four profiles that can be changed by the user, and one
factory default profile. The following table lists the syntax for the
commands involved in storing, recalling, and viewing profile
settings:
AT&Vn Views the settings in profile (n-1); n=0 to 5; n=0
views current settings.
AT&Wn Stores the current settings in user profile ‘n’; n=0 to 3.
ATZn Resets the current settings with the settings in profile
‘n’, n=0 to 4.
Profiles 0 to 3: User profiles.
Profile 4: Factory default profile.
Helpful Hints for PC Computers
Most PCs are equipped with more than one serial port. Standard
cables are readily available from many suppliers. Usually, serial
ports are manufactured in two forms, either with a 25-pin male jack
or a 9-pin male jack. For high speed serial connections at
230.4Kbps or 460.8Kbps, use a low-capacitance cable. Also, keep
the cable as short as possible.
The serial port is driven by interrupts. Every interrupt needs a
certain amount of overhead processing time. Too many interrupts
reduce the computer's efficiency. The UART 16450 is very
commonly used in serial port devices. For every character (byte)
received, it generates an interrupt. If your hardware allows it and if
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