Hello;
CVU was a a HMI program, DOS-Based, developped by Texas Instruments in the late 1980s to allow connections to its TI505 line of controllers; they communicated over TIWAY, a dedicates serial network used for TI505s.
Whatever information was available for such systems is to be found on Siemens USA site; for example: http://www.search.siemens.com/cgi-bin/search.asp?SCSconfig=WWW2SEASIEMENSCOM-SEA&q=CVU