Modem

Status

Indicates whether the port is in use by an application within the controller.

Options: In Use, Enabled

Factory default is Enabled

This is a read-only field

Driver

Mode

Can be either Local or RM.

A port used for a SCADA protocol must be set to emote.

WSOS or IOEX could be either Local or Remote according to the application.

Used By

Displays the application that has been assigned to this port e.g. WSOS, DNP3

If no application has been assigned this field will be blank.

This is a read-only field

Baud Rate

Configured for the baud rate at which this port is required to run.

Options: 300, 600, 1200, 4800, 9600, 19200, 38400, 57600, 115200

Factory default is 115200

Parity

The type of parity to be used by this port.

Options: None, Even, Odd

Factory default is None

Stop Bits

The number of stop bits to be appended to a transmitted byte.

Options 1, 2

Factory default is 1

RTS

Ready to Send

Determines whether RTS is asserted for the pre-transmission time prior to transmission of data as well as the post-transmission time after transmission.

Pre and post transmission RTS is required on most radio and modems.

Options: Enabled, Disabled

Factor default is Disabled

CTS

Clear to Send

If the modem does not support a CTS signal and/or the cabling has no CTS wiring then this setting must be set to CTS Ignore.

When set to CTS Ignore, the protocol asserts RTS as normal but does not check for a returned CTS input signal. If the modem supports a CTS signal, setting CTS to Don’t Ignore allows data to be transmitted only when CTS is asserted.

Option: Don’t Ignore, Ignore

Factory default is Ignore

DTR

Data Terminal Ready

If the modem supports DTR, this setting must be Enabled which will cause the DTR signal to be permanently asserted.

Options: Enabled, Disabled

Factor default is Disabled

Pre Transmission

If RTS support is Enabled, pre-transmission is the time delay between when RTS is asserted to when the message starts.

Range: 0...300 ms

Factory default is 250 ms

Post Transmission

If RTS support is Enabled, post-transmission is the time after the last character is sent before RTS is negated.

Range: 0...300 ms

Factory default is 35 ms

DCD

Data Carrier Detect

If the modem does not support a DCD signal this setting must be set to Ignore. Even if the modem does support DCD, this setting is usually set to Ignore.

This is because most point-to-point systems using conventional modems run as full duplex so that DCD is always asserted during normal operation. When set to DCD Ignore, the protocol will use any received data to build an incoming packet irrespective of DCD input signal. Also, the protocol will transmit irrespective of the DCD input signal.

If the modem supports DCD, this setting can be set to Don’t Ignore. When set to this mode, the protocol will only read data and build an incoming protocol packet when DCD is asserted. In addition, the protocol will not transmit when DCD is asserted. This is necessary for multi-dropped systems or ones shared with voice users or some radio modems.

Option: Don’t Ignore, Ignore

Factory default is Ignore

CA Delay

Collision Avoidance Delay

On a multi-drop communications link this setting can be used to provide priority access. If the controller prepares to transmit and finds that the link is busy (DCD asserted), it will wait until it is no longer busy, then wait for a back off time determined by:

Back off time = CA Delay + (random delay between zero and the CA Delay time)

After the back off time, the device will try again. If still unsuccessful, the controller will continue in an indefinite loop until it is successful.

If the DCD usage is configured for DCD Ignore, the CA Delay time is disabled.

Range: 0...180 000 ms

Factory default is 1000 ms.

Preamble

Determines whether the port transmits some preamble characters prior to transmitting a message. The message itself is not otherwise modified. Some modems require these characters to assist with message reception and synchronization at the master station. Start of frame filtering at the master station provides identification of the transmitted message.

Enabled means that the preamble characters are transmitted prior to a message transmission.

Disabled means that the message is transmitted without any preamble characters.

Options: Enabled, Disabled

Factory default is Disabled

First Character in Hex

This is the first character to be transmitted as a preamble. The character is specified by entering its ASCII code in hexadecimal format.

Range: 0x0 to 0xFF

Factory default is 55

Last Character in Hex

This is the last character that will be sent as part of the preamble. The character is specified by entering its ASCII code in hexadecimal format.

Range: 0x0 to 0xFF

Factory default is FF

Repeat First Character

This is the number of times the first character will be repeated as part of the preamble for example, if all preamble settings are at their default values, the preamble sent would be: 0x55, 0x55, 0x55, 0xFF