Lantronix MSS1-T, Reference Manual

Page: 41 / 117

Configuration Serial Port Configuration
4 - 7
4.4.4 Flow Control
NOTE: Flow Control is not available on the MSS485.
Both RTS/CTS (hardware) and XON/XOFF (software) flow control methods can be used on the
MSS. RTS/CTS controls data flow by sending serial port signals between two connected devices.
XON/XOFF controls data flow by sending particular characters through the data stream: Ctrl-Q to
accept data (XON) and Ctrl-S when data cannot be accepted (XOFF).
NOTE: Applications that use the control characters will conflict with XON/XOFF flow
control, in which case RTS/CTS is recommended.
To switch between flow control methods, use the Change Flow Control command followed by the
preferred method. If you do not wish to use flow control at all, specify None.
Figure 4-18: Enabling Recommended Flow Control
If you’re using XON/XOFF flow control, the XON/XOFF characters will be removed from the
data stream by default. To prevent this removal, the Passflow option can be enabled. However, it
will be unnecessary to enable Passflow in most situations. See Chapter 6, Commands, for more
information.
4.4.5 Modems and Modem Signalling
NOTE: Modem and Modem Signalling features are not available on the MSS485.
The following section details some of the MSS modem settings and modem signalling parameters.
These options are mutually exclusive. When you have finished configuring modem settings, refer
to the Modem Configuration Checklist on page B-5.
NOTE: Modem wiring issues are covered in Appendix C, Pinouts.
4.4.5.1 Modem Control
The MSS needs to know when the serial port is idle and when it is in use. If a connection has
ended, the MSS must logout the port and prepare to accept a new connection. If no connection is
open, the MSS must know to ignore spurious characters from the port and only accept valid
connection attempts. These two factors are governed by DSR/DTR signal handling.
The MSS is capable of DSR/DTR signal handling only when Modem Control is enabled. To enable
modem control, enter the Change Modem Control command.
Figure 4-19: Enabling Modem Control
4.4.5.2 Signal Checking
When a connection is lost, the MSS must log out the port and close any sessions. If it does not do
so, security problems may result when the next user logs in. The MSS uses the Data Signal Ready
(DSR) input signal to decide if there is a valid modem connection.
Local>> CHANGE FLOW CONTROL CTSRTS
Local>> CHANGE MODEM CONTROL ENABLED