Configuration Serial Port Configuration
4-10
The MSS supports Autobaud, which allows a serial port to match its speed to the attached serial device upon
connection (see Change Port [Portlist] Autobaud in the MSS Reference Manual for an explanation of the
baud rate negotiation process). Autobaud is disabled by default, but can be enabled with the following
command.
Figure 4-23: Enabling Autobaud
Character Size, Parity, and Stop Bits
The default character size of 8 data bits can be changed to 7 data bits. Similarly, the default stop bit count
of 1 bit can be changed to 2 bits. Parity is normally None, but can also be Even, Mark, Odd, or Space. To
change these parameters, use the following commands. Note that in this example, the parameters are being
changed for the second serial port only.
Figure 4-24: Configuring Serial Port Parameters
Flow Control
Note: RTS/CTS Flow Control is not available in RS-485 mode.
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 Ctrl-Q and Ctrl-S will conflict with XON/XOFF flow control, in
which case RTS/CTS is recommended.
To switch between flow control methods for a serial port, use the Change Port [Portlist] Flow Control
command followed by the preferred method. If you do not wish to use flow control at all, specify None.
Figure 4-25: 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, enable Passflow with the Change Port [Portlist] Passflow option.
However, passflow is unnecessary in most situations.
Modems and Modem Signaling
Note: These modem-related commands cannot be used with RS-485 networking.
The following sections explain some of the MSS options that are typically considered to be modem-related.
They do not apply exclusively to modems, but to communications devices in general. Most options are
mutually exclusive when enabled.
Local>> CHANGE PORT 1-4 AUTOBAUD ENABLED
Local>> CHANGE PORT 2 CHARSIZE 7
Local>> CHANGE PORT 2 STOPBITS 2
Local>> CHANGE PORT 2 PARITY EVEN
Local>> CHANGE PORT 2 FLOW CONTROL CTSRTS
or
Local>> CHANGE PORT 2 FLOW CONTROL XONXOFF
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