XBLOX gives an error that which states that a CAST symbol must be used. (The message may be tagged with one of several different error numbers.)
XBLOX 5.x has improve error checking over previous versions. One of the design-rule errors it now checks for is conflicting data types: busses with different data-type specifications coming from different places. These design-rule errors often slipped by versions of XBLOX previous to 5.0.
The CAST symbol is a symbol that translates a bus of one data type to a bus of another data type. The bus width is maintained; however, the index range may be different: e.g., 7:0 may be translated to 9:2. CAST may be placed in the schematic between any two XBLOX busses of different data types, and does not use any LCA resources. The CAST symbol is included in XBLOX libraries for XACT 5.0 and later. See the XBLOX User Guide (either the 1994 or 1995 editions) on p. 4-24 for more information on the CAST symbol.
For designs which use the obsolete library, the CAST symbol is not included in the XBLOX library. For the Viewlogic interface, it is included in the shm4000 library, which should be in your search path when processing existing XC4000 designs with XACT 5.x. OrCAD users will find this symbol on the BBS under cast_orc.zip. The Mentor symbol is automatically placed in the old libraries $LCA/blox directory on installation.