Channel Tag

Help Contents

Introduction

The Channel Tag is a SCADA/HMI communication channel to a PLC or other type of device.

There are two distinct types of channel tag:

Configuration Properties

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.

Dynamic Properties

The Channel Tag supports the dynamic 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 frame error occurs when a start or end character is not at its expected position.
IOErrorCount UDINT The total number of IO errors. An IO error is an error reported by the communication channel, for example parity and bit framing errors.

The State property can have these values:

StateDescription
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

Tag Commands

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.

Relationships to Other Tag Types

The Channel Tag builds on the features of these tag types:

The Channel Tag is used as a building block for these tag types:

Further Information

Core Tag

To learn about properties common to all tags.

Alarm Handling

To learn about alarm management.

Glossary

For the meaning of terms used in Fernhill SCADA.