3AT Commands, S-Registers and Result Codes
4.If your legacy software doesn’t have the correct modem initialization string, you must change it. AT&F^M, which selects the modem’s factory default settings, works well for most connections. (^M is the code for the carriage return character that sends the string to the modem.) If you need extra time to make a connection, add S7=60 to the string, like this: AT&FS7=60^M. For CompuServe, the initialization string should be AT&F\N0^M. If you use CompuServe’s WinCIM software, change the initialization string to AT&F\N0\Q1^M for compatibility with WinCIM’s software flow control. Change the error correction string to \N7%C0, and the data compression string to \N7%C1. If you want the modem to always answer the phone, add S0=1 to the initialization string.
∗: To change the modem’s default initialization string, type the new commands in the software’s terminal window, adding the command &W to store the new commands in the modem’s nonvolatile memory; e.g., AT&FS0=1&W. You can then simplify your initialization string to
ATZ^M.
5.If you are using legacy software, select the port the modem is connected to (normally, COM3).
6.For maximum throughput when using data compression, set the serial port baud rate, or DTE rate, to 115,200 bps. (In Windows 95, select Start, Settings, Control Panel, Modems, Properties.)
7.If your legacy software has an autobaud selection, make sure it is disabled. Autobaud is for much older modems, and can cause problems if enabled.
8.If the software allows you to edit the
(NO CARRIER, BUSY, NO ANSWER, NO DIALTONE), make sure there is no space between DIAL and TONE in
NO DIALTONE.
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