
MOTOROLA
Chapter 2. Register Model
2-23
Register Set
When an enabled data breakpoint condition matches with the address of a data access, a
DSI exception occurs. When a DSI exception is taken to indicate a data breakpoint
condition, DAR is set to the data address that causes the breakpoint and DSISR[9] is set.
The address of the instruction associated with the breakpoint condition is stored in SRR0.
Note that if the DABR/DABR2 register values are set to match on any exception vector, an
indeterminate or unrecoverable processor state may occur.
Table 2-15 describes the fields in DABR and DABR2.
A data address breakpoint match is detected for a load or store instruction if the following
conditions are met for any byte accessed:
EA0–EA28 = DABR[CEA]
MSR[DR] = DABR[BT]
The instruction is a store and DABR[WBE] = 1 or the instruction is a load and
DABR[RBE] = 1
Even if the above conditions are satisfied, it is undefined whether a match occurs in the
following cases:
A store conditional indexed instruction (
stwcx.
) in which the store is not performed
A load or store string instruction (
lswx
or
stswx
) with a zero length
A
dcbz
,
dcba
,
eciwx
, or
ecowx
instruction. For the purpose of determining whether
a match occurs,
eciwx
is treated as a load and
dcbz
,
dcba
, and
ecowx
are treated as
stores.
The cache management instructions other than
dcbz
and
dcba
never cause a match. If
dcbz
or
dcba
causes a match, some or all of the target memory locations may have been updated.
When a match occurs, a DSI exception is generated. Refer to Section 5.5.3, “DSI Exception
(0x00300),” more information on the data address breakpoint facility.
Table 2-15. Data Address Breakpoint Registers (DABR and DABR2) Bit Settings
Bits
Name
Description
0–28
CEA
Data address breakpoint
29
BT
Breakpoint translation enable. Match if MSR[DR] = DABR[BT].
30
WBE
Data write enable. Matching on data writes enabled.
31
RBE
Data read enable. Matching on data reads enabled.
F
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