The Channel Tag is a SCADA communication channel to any of the following:
There are two distinct types of channel tag:
The Channel Tag supports the configuration properties of the Alarm Tag, plus these properties:
| Property | Type | Version | Description |
|---|---|---|---|
| AlarmSeverity | UINT | 1.5 | The severity of the alarm raised when the channel fails. |
The Channel Tag supports the data properties of the Alarm Tag plus these properties:
| Property | Type | Description |
|---|---|---|
| State | UINT | The state of the channel |
| StateDescription | WSTRING | The text description of the channel state |
| FailedFunction | WSTRING | The I/O function call that caused the channel failure |
| ErrorMessage | WSTRING | The error returned by the failed I/O call |
| TxBytes | UDINT | The total number of bytes sent on the communication channel |
| RxBytes | UDINT | The total number of bytes received on the communication channel |
| DiscardedBytes | UDINT | The total number of bytes dropped due to communication errors |
| ReplyTimeoutCount | UDINT | The total number of requests that have received no reply |
| CRCErrorCount | UDINT | The total number of replies where the expected CRC did not agree with the CRC in the message. |
| FramingErrorCount | UDINT |
The total number of replies that were incorrectly framed.
A framing error can occur if:
|
| SequenceErrorCount | UDINT | The total number of replies where the sequence number does not match the request. This statistic only applies to protocols that use sequence numbers, for example Modbus TCP. |
| IOErrorCount | UDINT | The total number of I/O errors. An I/O error is an error reported by the communication channel, for example parity and bit framing errors. |
The State property can have these values:
| State | Description |
|---|---|
| 0 | The initial state of the channel before the driver starts. |
| 1 | A configuration error prevents further operation. |
| 2 | An unexpected I/O error occurred. |
| 3 | The channel has failed. |
| 4 | The channel is connecting. This is a temporary state. |
| 5 | The channel is disconnecting. This is a temporary state. |
| 6 |
The remote partner rejected the connection. For TCP/IP channels this means the TCP/IP connection succeeded, but in the initial protocol exchange the remote partner rejected the connection. |
| 15 | The channel is online and available for communications |
The Channel Tag supports the tag commands of the Alarm Tag plus this additional tag command:
| Tag Command | Version | Description |
|---|---|---|
| ResetStatistics | 3.7 | Resets the channel statistics back to zero. |
The Channel Tag builds on the features of these tag types:
The Channel Tag is used as a building block for these tag types:
To learn about properties common to all tags.
To learn about abnormal conditions in SCADA applications.
For the meaning of terms used in Fernhill SCADA.