Instrument Control Toolbox blocks should work perfectly for your usecase. As you are sending only one int16, data size [1 1] should be fine. I have attached Host Receive block and target send block settings. One thing to notice is that header and terminator settings are different in both the blocks. Target block need '' for header and terminator as highlighted in the attached picture.
Another thing to ensure is the GPIO settings in the Model Configuration Parameters. If you are using F28377S Launchpad, for SCI_A Tx is GPIO84 and Rx is GPIO85.
Hope this helps. Let me know.