ID:13929 VHDL syntax error at <location>: can't recognize character string <text>

CAUSE: In a VHDL Design File (.vhd), you used a character string at the specified location. However, Quartus Prime Integrated Synthesis cannot recognize the string because the string isn't a valid lexical element for VHDL. This error may occur because the string contains unsupported characters or characters that are supported only in specific contexts within a VHDL Design File. The string may also be an invalid identifier; for example, an identifier cannot start with an underscore (_) or contain consecutive underscores (for example, foobar_1 is legal, but foobar__1 is not).

ACTION: Check the specified location for typographical errors, unsupported characters, or invalid identifiers.