So being a tactical datalink, on ships they would be directly connected to the FCS systems of the various weapons? Is there a separate datalink for command structures?
Yes it's a tactical datalink !
As for direct feed of this data & its inter-operation with the FCS of the various weapons systems, think again.
Most modern warships (built in the last 5 -10 years) have an integrated command system, with Multi-function displays. The data from each of the sensors is fed, via an interface, into the command system. The datalink is no different.
The data is usually converted into an appropriate format, then overlayed on the radar / sensor display of the console. This provides the console operator the ability to view his processed data from the sensor he's using / in control of & see the corresponding information from the datalink.
The operator then usually has the facility to correlate "both tracks" (although sometimes this is a function of the software of the command system).
If the data is being used "to plot a solution", for a missile system, track data is passed back across the appropriate part of the interface to the Weapon System, & the console operator will be directed by the data on his screen, or by the Principal Warfare Officer (PWO) to engage the target.
I know that some systems are more likely classified as "stand alone", due to their ability to operate independently of the command system. However, they often still have a limited data link with the command system to relay bearing information, so that once the general direction of the target is provided, the "missile" can fire and then once in flight, the weapon can control how it attacks the target.
Systems Adict