
MOTOROLA
Chapter 5. Exceptions
5-29
Exception Definitions
The operand of a
eciwx
or
ecowx
instruction is not aligned
The operand of a
dcbz
instruction is in a page that is write-through or
caching-inhibited
Note that although the MPC603e processor generates an aligment exception for a
misaligned little-endian access (MSR[LE] = 1), the G2 core does not.
The register settings for alignment exceptions are shown in Table 5-15.
The architecture does not support the use of a misaligned EA by
lwarx
or
stwcx.
instructions. If one of these instructions specifies a misaligned EA, the exception handler
should not emulate the instruction, but should treat the occurrence as a programming error.
5.5.6.1
Integer Alignment Exceptions
The G2 core is optimized for load and store operations that are aligned on natural
boundaries. Operations that are not naturally aligned may suffer performance degradation,
Table 5-16. Alignment Interrupt—Register Settings
Register
Setting
SRR0
Set to the effective address of the instruction that caused the exception
SRR1
0–15
16–31 Loaded from MSR[16–31]
Cleared
MSR
POW 0
TGPR 0
ILE
EE
PR
—
0
0
FP
ME
FE0
SE
BE
0
—
0
0
0
FE1
CE
IP
IR
DR
0
—
—
0
0
RI
LE
0
Set to value of ILE
DSISR
0–11
12–13 Cleared. (Note that these bits can be set by several 64-bit PowerPC instructions that are not
supported in the G2 core.)
14
Cleared
15–16 For instructions that use register indirect with index addressing—set to bits 29–30 of the
instruction
For instructions that use register indirect with immediate index addressing—cleared
17
For instructions that use register indirect with index addressing—set to bit 25 of the instruction
For instructions that use register indirect with immediate index addressing—set to bit 5 of the
instruction
18–21 For instructions that use register indirect with index addressing—set to bits 21–24 of the
instruction
For instructions that use register indirect with immediate index addressing—set to bits 1–4 of
the instruction
22–26 Set to bits 6–10 (identifying either the source or destination) of the instruction. Undefined for
dcbz
.
27–31 Set to bits 11–15 of the instruction (
r
A).
Set to either bits 11–15 of the instruction or to any register number not in the range of registers
loaded by a valid form instruction, for
lmw
,
lswi
, and
lswx
instructions. Otherwise undefined.
Cleared
DAR
Set to the EA of the data access as computed by the instruction causing the alignment exception.
When the operand of an
lmw
,
stmw
,
lwarx
, or
stwcx.
instruction is not word-aligned, that address
value + 4 is stored into the DAR.
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.