Since the version D2000 v7.1.0, release A050525000, there has been implemented a new ASDU 252 into the communication protocols IEC 870-5-104 and IEC 870-5-104 Server. The ASDU 252 allows a data transmission between two D2000 Systems, one of them uses the protocol IEC 870-5-104 and the other one uses IEC 870-5-104 Server.
ASDU 252 should be used if you need to transfer:

• values along with their user attributes (flags),
• values of Text, Relative time and Absolute time type,
• analog values with the 32-bit accuracy,
• values of basic object attributes ValueLimitStatus and/or ValueProcAlarmStatus (very rarely).

Required configuration

• the types of output I/O tag and respective input I/O tag must be the same (Ao-Ai, Dout-Di, TxtO-TxtI, ...)
• configuration of output I/O tag must be set to ASDU 252 (the tab Address, the parameter ASDU type)

Communication station parameters:

Keyword	Full name	Meaning	Unit	Default value
D2CLS	D2000 Copy Limit Status	The parameter is set on the station that is the parent of input I/O tags for which the partner station sends ASDU 252. Such I/O tag then ignores its defined limits and copies the ValueLimitStatus (basic object attribute) of its control object. If there are configured process alarms for input I/O tag, they will be evaluated according to the ValueLimitStatus copied from the control object. Note: The parameter D2VCO must be set on the partner station.	-	False
D2CPA	D2000 Copy Process Alarms	The parameter is set on the station that is the parent of input I/O tags for which the partner station sends ASDU 252. Such I/O tag then ignores its configuration and copies process alarms of the control object of partner output I/O tag. Note: The parameter D2VCO must be set on the partner station.	-	False
D2VCO	D2000 ASDU Value from Control Object	The parameter is set on the station that is the parent of output I/O tags with defined ASDU 252. If a control object is defined for such I/O tag, then the value of the control object is sent to communication as the output value (along with its basic object attributes - ValueType, ValueTime, ValueStatus, ValueLimitStatus, ValueProcAlarmStatus, ...). Warning: In this case, there are ignored all configuration of output I/O tag concerning process alarms, limits and value conversion ! Value of output I/O tag seems to be correct within D2000 system, but there is sent "raw" value of control object into communication. Note: To send "raw" value of control object, the value types of control object and output I/O tag must be the same, otherwise there is sent ordinary output value.	-	False

Notes:

• The parameters D2CLS and D2CPA allow getting values of process alarms and ValueLimitStatus of control object only (not given I/O tag) - because process alarms and ValueLimitStatus of I/O tag are being set after its writing.
• Implemented functionality (combination of the parameters D2CLS, D2CPA and D2VCO) may cause the value of output I/O tag to be "inconsistent" (e.g. value is in IN_LIMIT status and there is the process alarm HL active at the same time). !!! WE RECOMMEND TO  USE IT CAREFULLY !!!