3 AT Commands
CommPlete Communications Server 21

&Fn Load Default Configuration

n
= 0, 8, or 9
Default: &F8
MT3334HD8 modems store factory default AT command settings and S-register values i n read-only
memory (ROM); they store your custom AT command and S-register values in nonvo latile random access
memory (NVRAM).
The &F0 (or &F) command resets the modem to the factory default values stored in ROM or to your
custom values stored in NVRAM, depending on whether you last stored an &F8 or an &F9 command.
When &F8 is stored and an &F command is issued, the modem reads the factory default settings stored in
ROM.
When &F9 is stored and an &F command is issued, the &W setting determines whether the modem reads
settings stored in NVRAM or ROM. If the modem is set to &W0, it reads your custom settings stored in
NVRAM. If the modem is set to &W1, it erases your stored settings (including the &F9 command) and
reads the factory default settings stored in ROM. Many communications programs issue the &F command
automatically—the &F9 command allows you to select your own defaults.
Note that for either an &F8 or an &F9 command to be effective after a reset it must be stored using the
&W0 command.
Table 2 summarizes how the &F and Z reset commands interact with the &W command; note that the &F
reset command operates differently from the Z reset command:

Table 2. Where the Modem Reads Configuration Parameters

Previous Command AT&F Pow er-On and ATZ
AT&W1 (default) ROM ROM
AT&W0 ROM NVRAM
AT&F8&W0 ROM NVRAM
AT&F9&W0 NVRAM NVRAM

Z Reset Modem

The Z command resets the modem to its default configuration and clears the command buffer. The result
is the same as turning the modem off and on. When you type ATZ, the state of the &W command
determines where the default values originate. &W0 defaults come from the customized configuration in
NVRAM, and &W1 defaults come from the factory default configuration in ROM. Because Z clears the
command buffer, it must be the last command in a command string; normall y it is issued by itself: ATZ.
Note that the Z reset command operates differently from the &F reset command. See Table 2 on page 21.
Modem Response (Result Code) Commands
The MT3334HD8’s modems can give responses to commands. The most common one is
OK
, but the
modems also can alert you or your software to dial tones, busy signals, connection speeds, and whether the
connection is made with error correction or compression enabled. These responses are called

result codes

,
and they can be terse or verbose, Multi-Tech or standard, basic or extended.