Serial Port Flow Control - \Q - Motorola V.3600 User Manual

Serial Port Flow Control — \Q
The \Q commands set the type of flow control used by the serial port. If
the serial port speed exceeds that of the modem connection, characters
may be sent by the DTE to the modem faster than it can send them to the
remote modem. The modem holds characters in an internal buffer until
they can be transmitted. When this buffer is full, the modem uses flow
control to stop data from the DTE. As the modem continues to transmit
data and the buffer empties, flow control is again used to cause the DTE
to resume sending data.
• The \Q - \Q3 commands affect both DTE and DCE flow control.
• The \Q4 - \Q7 commands affect only flow control by the DCE.
• The \Q command disables flow control bilaterally.
When the \Q1 command is used, the modem generates and accepts
XON/XOFF characters to start and stop the data flow. These characters
have the same parity as the DTE setup taken from the last AT command.
When the \Q2 command is used, the modem uses CTS off to stop the
data from the DTE and CTS on to restart it.
When the \Q3 command is used, the modem uses CTS off to stop the
data from the DTE and CTS on to restart it. The DTE uses RTS off to
stop data from the modem and RTS on to restart it.
The \Q4 command disables flow control by the DCE.
The \Q5 command enables XON/XOFF flow control by the DCE only.
The \Q6 and \ Q7 commands force the modem to use RTS off to stop
data from the modem and RTS on to restart it. This does not affect DTE
flow control.
Command
\Q
\Q1
\Q2
\Q3
\Q4
\Q5
\Q6
\Q7
Operation
Disable bilateral flow control
Enable bilateral XON/XOFF flow control
Enable DTE CTS flow control, disable DCE flow control
Enable CTS/RTS bilateral flow control
Disable DCE flow control
Enable DCE XON/XOFF flow control
Enable DCE RTS flow control
Enable DCE RTS flow control
V.3600
Protocols
6-7