MOTOROLA
5-16
CENTRAL PROCESSING UNIT
MC68331
USER’S MANUAL
5
Each vector is assigned an 8-bit number. Vector numbers for some exceptions are ob-
tained from an external device; others are supplied by the processor. The processor
multiplies the vector number by four to calculate vector offset, then adds the offset to
the contents of the VBR. The sum is the memory address of the vector.
5.9.2 Types of Exceptions
An exception can be caused by internal or external events.
An internal exception can be generated by an instruction or by an error. The TRAP,
TRAPcc, TRAPV, BKPT, CHK, CHK2, RTE, and DIV instructions can cause excep-
tions during normal execution. Illegal instructions, instruction fetches from odd ad-
dresses, word or long-word operand accesses from odd addresses, and privilege
violations also cause internal exceptions.
Table 5-2 Exception Vector Assignments
Vector
Number
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16–23
Vector Offset
Dec
Hex
0
4
8
12
00C
16
20
24
28
01C
32
36
40
44
02C
48
52
56
60
03C
64
92
05C
96
100
104
108
06C
112
116
120
124
07C
128
188
0BC
192
232
0E8
236
252
0FC
256
1020
Assignment
Space
SP
SP
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
SD
000
004
008
Reset: Initial Stack Pointer
Reset: Initial Program Counter
Bus Error
Address Error
Illegal Instruction
Zero Division
CHK, CHK2 Instructions
TRAPcc, TRAPV Instructions
Privilege Violation
Trace
Line 1010 Emulator
Line 1111 Emulator
Hardware Breakpoint
(Reserved, Coprocessor Protocol Violation)
Format Error and Uninitialized Interrupt
Format Error and Uninitialized Interrupt
(Unassigned, Reserved)
010
014
018
020
024
028
030
034
038
040
24
25
26
27
28
29
30
31
060
064
068
SD
SD
SD
SD
SD
SD
SD
SD
SD
Spurious Interrupt
Level 1 Interrupt Autovector
Level 2 Interrupt Autovector
Level 3 Interrupt Autovector
Level 4 Interrupt Autovector
Level 5 Interrupt Autovector
Level 6 Interrupt Autovector
Level 7 Interrupt Autovector
Trap Instruction Vectors (0–15)
070
074
078
32–47
080
48–58
0C0
SD
(Reserved, Coprocessor)
59–63
0EC
SD
(Unassigned, Reserved)
64–255
100
3FC
SD
User Defined Vectors (192)