
MOTOROLA
MC68330 USER'S MANUAL
5- 79
15
0
SP
STATUS REGISTER
+$02
PROGRAM COUNTER HIGH
PROGRAM COUNTER LOW
+$06
0000
VECTOR OFFSET
Figure 5-21. Format $0 — Four-Word Stack Frame
5.6.4.2 SIX-WORD STACK FRAME. This stack frame (see Figure 5-22) is created by
instruction-related traps, which include CHK, CHK2, TRAPcc, TRAPV, and divide-by-zero,
and by trace exceptions. The faulted instruction PC value is the address of the instruction
that caused the exception. The next PC value (the address to which RTE returns) is the
address of the next instruction to be executed.
15
0
SP
STATUS REGISTER
+$02
NEXT INSTRUCTION PROGRAM COUNTER HIGH
NEXT INSTRUCTION PROGRAM COUNTER LOW
+$060010
VECTOR OFFSET
+$08
FAULTED INSTRUCTION PROGRAM COUNTER HIGH
FAULTED INSTRUCTION PROGRAM COUNTER LOW
Figure 5-22. Format $2 — Six-Word Stack Frame
Hardware breakpoints also utilize this format. The faulted instruction PC value is the
address of the instruction executing when the breakpoint was sensed. Usually this is the
address of the instruction that caused the breakpoint, but, because released writes can
overlap following instructions, the faulted instruction PC may point to an instruction
following the instruction that caused the breakpoint. The address to which RTE returns is
the address of the next instruction to be executed.
5.6.4.3 BERR STACK FRAME. This stack frame is created when a bus cycle fault is
detected. The CPU32 BERR stack frame differs significantly from the equivalent stack
frames of other M68000 Family members. The only internal machine state required in the
CPU32 stack frame is the bus controller state at the time of the error and a single register.
Bus operation in progress at the time of a fault is conveyed by the SSW.
15
14
13
12
11
10
9876543210
TP
MV
0
TR
B1
B0
RR
RM
IN
RW
LG
SIZ
FUNC
The BERR stack frame is 12 words in length. There are three variations of the frame, each
distinguished by different values in the SSW TP and MV fields.
An internal transfer count register appears at location SP + $14 in all BERR stack frames.
The register contains an 8-bit microcode revision number, and, for type III faults, an 8-bit
transfer count. Register format is shown in Figure 5-23.
15
8
7
0