User's Manual

\N – Set Operating Mode
Determines the type of connection attempted by the modem.
AT\N0,1 Buffer (Normal) Mode – no data compression or error correction, but
uses speed buffering.
AT\N2 MNP Reliable Mode – the modem attempts to negotiate an MNP
error-correction ’reliable’ link, hanging up if it fails.
AT\N3 V.42 Auto-Reliable Mode – if V.42 detection is enabled (-Jn), a
LAPM or MNP link can be detected and negotiated; otherwise, only
LAPM is attempted. If configured for -J0 and a protocol connection is
not made, the modem hangs up. If configured for -J1 and a protocol
connection is not made, the modem falls back to speed buffering
mode.
AT\N4 V.42 Reliable Mode – the modem attempts to negotiate LAPM error
correction, hanging up if it fails
=> Some types of modem will not accept an MNP connection. In such
cases, use the \N0 command (Buffering) or the \N1 command (Direct mode).
\Q – Set Serial Port Flow Control
This command specifies the DTE-to-modem flow control. Software flow control
uses the XOFF (13h) command to stop and the XON (11h) characters to start
data transmission, both to and from DTE. Undirectional hardware flow control
uses the CTS control line to stop or start data from the DTE only, while bi-
directional hardware flow control also uses the RTS control to stop or start
data from the modem.
AT-Q0 Disables flow control
AT-Q1 XON/XOFF software flow control
AT-Q2 Undirectional hardware flow control – CTS
AT-Q3 Bi-directional hardware flow control – RTS/CTS
=> The advantage of the RTS/CTS-Hardware flow control in opposite of the
XON/ XOFF Software flow control is the short reactiontime. The reactiontime is
for the binary date transfer, which can contain XON/XOFF-settings, absolute
necessary.
2-18 AT COMMANDS: DATA MODEM