Serial Port Mode String

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Introduction

Certain tag types support a Mode string that defines the communication parameters of a serial port.

The Serial Port Mode String consists of a list of parameter and value pairs, which configure a serial port. For example:

Baud=9600 Parity=E Data=7 Stop=1

Note: This represents a data rate (baud) of 9600 bits per second, Even parity, 7 data bits and 1 stop bit.

The keywords you can use in Mode strings, and the allowed values, are described in this table:

ParameterValuesDefaultDescription
baud 110, 300, 600, 1200, 2400, 4800, 9600, 14400,
19200, 38400, 57600, 115200, 128000, 256000
9600 Baud rate (bits per second)
parity E, O, M, S, N N The parity check bit added to the data.
N = No parity.
E = Even parity.
O = Odd parity.
M = Mark parity.
S = Space Parity.
data6, 7, 88The number of data bits in each character
stop1, 22The number of stop bits at the end of each character
xonon, offoffWhether the xon/xoff protocol for data flow control is on, or off
dtr on, off, hs on  Whether Data Terminal Ready (DTR) signal is set to on, or off, or handshake.
Off = DTR signal is off.
On = DTR signal is on.
Hs = DTR handshaking is enabled.
octs on, off off Whether the Clear To Send (CTS) signal is monitored for output flow control.
Off = Data is sent regardless of the state of the Clear To Send (CTS) signal.
On = Data is only sent if the Clear To Send (CTS) signal is On.
odsr on, off off Whether the Data Set Ready (DSR) signal is monitored for output flow control.
Off = Data is sent regardless of the state of the Data Set Ready (DSR) signal.
On = Data is only sent if the Data Set Ready (DSR) signal is On.
rts on, off, hs, tg on Whether Request To Send (RTS) signal is set to on, or off, or handshake, or toggle
Off = RTS signal is off.
On = RTS signal is on.
Hs = RTS signal is on when the input buffer is less than 50% full. RTS signal is off when the input buffer is more than 75% full.
Tg = RTS signal is on when there are bytes available for transmission.
idsr on, off off Whether received data is ignored if the Data Set Ready (DSR) signal is off.
Off = All received data is processed regardless of the state of DSR.
On = Received data is processed only if the DSR signal is on.

Note: Not all PC hardware supports all of the options described above. Please refer to the serial port manufacturers data sheet(s) for details of which options may or may not be supported.

Further Information

Serial Communications

For background information on serial communications.

Serial Port Mode Editor

For information about the dialog editor for serial port mode strings.

Glossary

For the meaning of terms used in Fernhill SCADA.