A24 window size too large for crates with many slots
[reported by David Cobas]
In certain CERN crates, we may have more than 15 cards addressed in A24 mode. The current window size of the SVEC in A24 mode is 0x100000, allowing for up to 15 cards only. Reducing the size to 0x80000 (or making it a generic in the VHDL instantiation) would eliminate the possibility of address conflicts.