Black Box 3600 MODEM manual Serial Port Flow Control \Q

Models: 3600 MODEM 3600

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Protocols

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

Operation

 

 

\Q

Disable bilateral flow control

 

 

\Q1

Enable bilateral XON/XOFF flow control

 

 

\Q2

Enable DTE CTS flow control, disable DCE flow

 

control

 

 

\Q3

Enable CTS/RTS bilateral flow control

 

 

\Q4

Disable DCE flow control

 

 

Modem 3600

6-7

Page 109
Image 109
Black Box 3600 MODEM manual Serial Port Flow Control \Q