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User's Guide
Follow the steps below to change the modem initialization string. Refer to the PX5 or
4400 User’s Guide, Chapter 4 Instrument Settings – Communications, for the PX5/4400
screen interface.
1. From the PX5/4400 Communications Settings screen used to configure modem
connection speed, click on the Change button to the right of the string field display.
2. Use the virtual keypad that appears on the screen to change and enter the new string
command. The modem initialization string commands for the Conexant (Rockwell)
chipset and the Agere (Lucent) chipset are discussed in the next section.
3. When done, click on OK to accept changes in modem communications settings.
Modem Initialization String Command
The following is the AT initialization string for a modem using the newer Conexant
(Rockwell) chipset:
AT&F;S0=2;+IFC=0,0;S30=6
Where:
AT is the modem attention command
&F instructs the modem to restore factory configuration
S0=2 turns auto-answer on and sets the number of rings to answer to two.
+IFC=0,0 turns flow control off.
S30=6 sets a 60 second inactivity modem hang up timeout.
; is a command delimiter.
NOTE: It may be necessary to adjust the modem connection speeds to specify a
minimum baud rate. This is possible using the +MS modem command. Check the
modem manual for use of the +MS command. There are several varieties of the
command. Typically, a modem modulation scheme and minimum and maximum transmit
and receive speeds can be specified. Using Hyperterminal, it is possible to get a list of
the possible command ranges and syntax by typing AT+MS=?.
The following is the AT initialization string for a modem using the Agere (Lucent) chipset:
AT&F;S0=2;&K0;%E0;S30=6
Where:
AT is the modem attention command.
&F instructs the modem to restore factory configuration.
S0=2 turns auto-answer on and sets the number of rings to answer to two.
&K0 turns flow control off.
%E0 disables baud rate fall back/fall forward.
S30=6 sets a 60 second inactivity modem hang up timeout.
; is a command delimiter.
A similar note regarding connect speeds applies. Try using the AT-V90= command and
modifying the contents of S registers S37 and S38.
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