DCW directive allocates one or more halfwords
of memory, aligned on two-byte boundaries, and defines the initial
runtime contents of the memory.
DCWU is the same, except that the memory alignment
is a numeric expression that evaluates to an integer in the range -32768 to 65535.
DCW inserts a byte of padding before the first
defined halfword if necessary to achieve two-byte alignment.
DCWU if you do not require alignment.