Instrument WriteValue Method is used to change the value of the ProcessVariable in an instance of MDISInstrumentOutObjectType. The Instrument WriteValue Method operation applies to the object in the subsea system. The value of the ProcessVariable value will only update once the subsea system has provided a new value. Some systems will be able to report any errors immediately others will only be able to report that the operation was not refused. Clients are expected to monitor the ProcessVariable and ensure that the operation completed successfully. If an error occurs after the Method has returned, a Fault flag shall be set and an appropriate FaultCode will be returned. The Fault (and FaultCode) will reset on the next successful Instrument WriteValue Method invocation.

Signature:

WriteValue (

[in] 0:Float Value);

Table 33 – WriteValue Method parameters

Argument	Description
Value	Float value Variable, that indicates the target state of the Variable

Method result codes are defined as part of the Call Service (see OPC 10000-4). They are described in Table 124 for ease of reference.

Comments

The WriteValue Method will result in a change the value of the ProcessVariable Variable. The Method will report if any error occurs while writing the value of the Object. Table 34 specifies the AddressSpace representation for the WriteValue

Table 34 – WriteValue Method AddressSpace Definition

Attribute	Value
BrowseName	WriteValue
References	Node Class	BrowseName	DataType	TypeDefinition	Other
0:HasProperty	Variable	0:InputArguments	0:Argument[]	0:PropertyType	M
ConformanceUnits
MDIS Instrument Out Base