AR# 10859: 4.1i XST - XST does not support "predefined attribute" VHDL expressions.
4.1i XST - XST does not support "predefined attribute" VHDL expressions.
Keywords: attribute, predefined, VHDL, XST
General Description: In VHDL, predefined attributes can be useful when you are managing arrays. A small list of these attributes (not comprehensive) follows:
X'left(N) X'right(N) X'range(N) X'length(N)
where "X" refers to the array type or object (commonly a signal) and "N" refers to a number from 1 to the size of the array "X". If no "N" is mentioned, the default is assumed to be the maximum size of "X."
These predefined arrays are not supported in 4.1i XST. (Support for predefined arrays was added in the 5.1i software release.)
There is no VHDL code mentioned here because predefined attributes may be used in a variety of ways. You can work around this limit by being explicit, either using generics or by passing the actual value.
The predefined attributes listed above are supported in the 5.1i XST release.