Remote Row Edit: Scan Parameters tab

Fast Scan Duration (sec)

Enter the length of time (in seconds) that the remote should remain on fast scan mode after the system issues the fast scan function put. Fast scan is a method of setting a remote to interrogate mode for a set time period. In interrogate mode, the remote is polled more frequently than in a normal poll cycle; therefore, updates are received more quickly. The system automatically places a remote on fast scan after the former issues an analog setpoint or digital output command. This ensures that the command feedback is received as soon as possible. Remotes can be placed into timed interrogate mode through the Remote Control dialog box. For more information, refer to the AVEVA Enterprise SCADA HMI Controller documentation. Remotes on fast scan mode are not affected by the RTU Poll Delay setting.

Timeout for No-reply Alarm (sec)

Enter the number of seconds the system should wait since the last normal poll cycle before generating a NO REPLY alarm.

If the data is not received from the remote after a specified number of retries, the remote shifts to the NO REPLY state. If the Timeout for No-reply Alarm (sec) value is exceeded, the system generates a NO REPLY alarm.

See Also: Hold-Off Alarms.

Timeout for Invalid Msg Alarm (sec)

Enter the number of seconds the system should wait since the last normal poll cycle before generating an INVALID MESSAGE alarm.

If an invalid message is received from the remote after a specified number of retries, the remote shifts to the INVALID MESSAGE state. If the Timeout for Invalid Msg Alarm (sec) value is exceeded, the system generates an INVALID MESSAGE alarm.

See Also: Hold-Off Alarms.

Timeout for Line Failure Alarm (sec)

Enter the number of seconds the system should wait since the last normal poll cycle before generating a LINE FAILURE alarm.

If the remote stays in this state for longer than the Timeout for Line Failure Alarm (sec) value, the system generates a LINE FAILURE alarm.

See Also: Hold-Off Alarms.

RTU Poll Delay (HH:MM:SS)

Enter the time interval that passes between device polls.

Using a poll delay reduces the bandwidth wasted on remotes that return less important data. The delay can also help reduce polls of battery-operated remotes.

If the remote is not responding, then the effective RTU poll delay is the greater of the following two values: RTU Poll Delay or No Response Delay.

This delay setting is overridden if the remote is placed on fast scan or interrogate mode (refer to AVEVA Enterprise SCADA HMI Controller documentation). The RTU Poll Delay is configured for the following reasons:

• To reduce the amount of bandwidth wasted by non-critical remotes or remotes that transfer data that rarely change.

• To reduce load on the CPU.

• To prevent frequent polling of battery-operated remotes.

• To minimize phone line charges that are based on traffic or amount of data sent.

To view an example, refer to RTU Poll Delay example below.

RTU Intra-poll Delay (ms)

The delay period (in milliseconds) between successive access attempts to a remote. The delay period may be between, for example, poll ranges, and/or digital commands, setpoints, or gas history uploads.

The usage of this configuration is protocol-specific.

No Response Delay (HH:MM:SS)

Enter the time interval that passes between poll attempts after a no response is received from the remote.

When no response is received from the remote over the connection it currently uses, the Omnicomm process attempts to poll the remote at an interval equal to the greater of the following two values:

• The value specified in the RTU Poll Delay field.

• The value specified in the No Response Delay field.

This occurs whether or not the problem is with the remote itself or its communication path.

Other reasons for adding a No Response Delay are:

• To reduce the amount of bandwidth wasted by non-critical remotes or remotes that transfer data that rarely change.

• To minimize phone line charges that are based on traffic or amount of data sent.

To view an example, refer to No Response Delay example below.

RTN Alarm Inhibit (poll cycles)

Enter the number of successful poll cycles that must be completed before the system issues a Return-to-Normal alarm that indicates communication with this remote has returned to normal from an abnormal state.

This reduces spurious alarming in situations where communication with a remote is sporadic. Return-to-Normal alarming works similarly to no-reply timeout.

Cryout Modem Bank

Select (...) and select the modem bank (Mbank) record used by the remote.

This field only needs to be configured for systems or projects with cryout connections.

RTU Turnaround Time (ms)

Enter the time (in milliseconds) it takes for the remote to parse a query (not a command), process it and formulate a response.

There is no typical value for this field; it can take anywhere from 1 to 100 milliseconds depending on the firmware and CPU load of a given brand of remote.

For more information, refer to RTU turnaround time and overhead time delays.

Overhead Processing Time (ms)

Enter the time (in milliseconds) to be added to the RTU Turnaround Time to calculate the maximum time required to receive a response from the remote.

This is used to accommodate remotes that require more time to execute commands than to respond to data queries. This applies only to some commands that are sent to the remote (for example, setpoints, digital outputs).

For more information, refer to RTU turnaround time and overhead time delays.

Protocol Driver Specific Retries

This field is only used by certain protocol drivers. If the driver is not supported by the protocol, this field is ignored.

Poll Timeout Enable

Select to have the system generate an alarm on the remote when it exceeds the maximum poll time, as indicated in the Poll Timeout (sec) field.

For further information, refer to Poll Time Exceeded Alarm.

Poll Timeout (sec)

Enter the poll timeout value in seconds. When the poll delta time exceeds this value, AVEVA Enterprise SCADA generates an alarm.