WriteValue Method (defined in Table 11) is used to change the value of the State Variable in an instance of MDISDiscreteOutObjectType. The WriteValue operation applies to the object in the subsea system. The value of the State Variable shall only be updated once the subsea system has provided a new value. For Objects that are used as a command, the value of the State Variable shall be updated directly to the value provided by the State parameter of the Method. 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 State and ensure that the operation completed. 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 WriteValue Method invocation.

Signature:

WriteValue (

[in] 0:UInt32 State);

Table 11 – WriteValue Method parameters

Argument	Description
State	UInt32 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 State Variable. The Method will report if any error occurs while writing the state of the Object. Table 12 specifies the AddressSpace representation for the WriteValue Method.

Table 12 – WriteValue Method AddressSpace Definition

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