AT Commands
F-46 AT Commands
\Q
n Serial Port Flow Control
\Q0
Disables flow control.
\Q1
Enables bi-directional XON/XOFF flow control.
\Q2
Enables unidirectional hardware flow control; the modem uses CTS to control the
terminal.
\Q3
Enables bi-directional hardware flow control.
\Q4
Enables unidirectional XON/XOFF flow control.
\Q5
Keeps CTS Off until connection for unidirectional hardware flow control
\Q6
Keeps CTS Off until connection for bi-directional hardware flow control; ignores RTS
until connection.
Sets the type of flow control used on the serial port. If the serial port speed is faster
than the modem port speed, data from your computer enters the modem faster than it
leaves. The modem holds characters in a buffer and sends them out at the slower
modem port bps rate. When the buffer is full, flow control instructs your computer to
stop transmitting data to the modem; the modem continues to send out the characters
and empty the buffer. When there is room in the buffer, flow control instructs your
computer to resume transmitting data to the modem.
For reliable connections, retransmissions can reduce the effective modem port speed.
If this occurs, flow control prevents buffer overflow.
During direct mode connections, the modem does not use flow control and ignores the
\Q setting.
NOTE
Hardware flow control overrides the &C and \D settings for CTS operation.
\Q1: Enables bi-directional XON/XOFF flow control. Sending an XOFF character
stops data transmission; sending an XON character restarts it. The modem generates
XON and XOFF characters at the same parity as on the serial port. The serial port
responds to XON and XOFF characters from the local computer in the same way.
\Q2: Enables unidirectional hardware flow control. The modem turns CTS Off to
signal the local computer to stop transmitting data, and turns CTS On to signal the local
computer to resume transmitting data.
\Q3: Sets bi-directional hardware flow control using the CTS and RTS signals. The
modem uses the CTS signal to start and stop data transmission from the local
computer. When RTS is Off, the modem stops transmitting data to the local computer.
When RTS is On the modem resumes sending data.
