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Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

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270 <strong>Practical</strong> Modern <strong>SCADA</strong> Protocols: DNP3, <strong>60870</strong>.5 <strong>and</strong> <strong>Related</strong> <strong>Systems</strong><br />

Type 103 Clock synchronization comm<strong>and</strong><br />

INFORMATION OBJECT TYPE: 103<br />

CODE:<br />

C_CS_NA_1<br />

DESCRIPTION:<br />

Clock synchronization comm<strong>and</strong><br />

VALID WITH SQ: 0<br />

Information Object for SQ = 0 (Sequence of Information Objects)<br />

Single information object only.<br />

Information Object Address<br />

IOA = 0<br />

CP56Time2a<br />

Seven-octet binary time<br />

Valid cause of transmission codes<br />

In control direction<br />

Activation<br />

In monitor direction<br />

Spontaneous<br />

Activation confirmation<br />

Unknown type identification<br />

Unknown cause of transmission<br />

Unknown common address of ASDU<br />

Unknown information object address<br />

Notes<br />

This comm<strong>and</strong> may be used in the monitor direction to transmit the outstation clock time.<br />

This enables messages stored at an outstation that span a change of hour to be interpreted<br />

without ambiguity. This arises because three-octet binary time provides only minutes <strong>and</strong><br />

milliseconds up to one hour. Therefore, to interpret correctly time-tags from outstations,<br />

it is necessary to include outstation time hour changes within the messages. It is also<br />

necessary for the master station to keep a track of outstation hour whilst sequentially<br />

processing stored time-tagged data.

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