0 - AlwaysInAdvise

The I/O Block is updated if the AllowRead property is set to True

1 - AdviseWhenLinked

The I/O Block is updated only if the AllowRead property is set to True, and the I/O Block is associated to an active object, that is, one Display on an open Screen or an enabled Alarm, among others. An I/O Block link for this purpose can be assigned to the Value, RawValue, Quality, and from Bit00 to Bit31 for I/O Block Element properties, and Quality and TimeStamp for I/O Block properties (default)