5.2.5 Vector Base Register (VBR)
The VBR contains the base address of the 1024-byte exception vector table, consist-
ing of 256 exception vectors. Exception vectors contain the memory addresses of rou-
tines that begin execution at the completion of exception processing. Refer to 5.9
Exception Processing for more information on the VBR and exception processing.
5.3 Memory Organization
Memory is organized on a byte-addressable basis in which lower addresses corre-
spond to higher order bytes. For example, the address N of a long-word data item cor-
responds to the address of the most significant byte of the highest order word. The
address of the most significant byte of the low-order word is N + 2, and the address of
the least significant byte of the long word is N + 3. The CPU32 requires long-word and
word data and instructions to be aligned on word boundaries (refer to Figure 5-6).
Data misalignment is not supported.
5
MC68331
CENTRAL PROCESSING UNIT
MOTOROLA
5-7
USER’S MANUAL
MOTOROLA [ MOTOROLA ]
