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G2 PowerPC Core Reference Manual
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MOTOROLA
Implementation-Specific Information
1.3.8.2
Data Address Breakpoint Registers (DABR and DABR2)
DABR and DABR2 cause a breakpoint exception (subset of the DSI exception) if there is
a match between the CEA field and the address of any data access and the data breakpoint
is enabled. DABR[CEA] and DABR2[CEA] hold an effective address to which each data
access address is compared. In addition, data breakpoints are enabled for write and read
accesses individually by setting bit 30 and bit 31 of the DABR, respectively. Finally, the
data address breakpoint translation bit (DABR[BT]) must match MSR[DR] for a match to
occur.
The data access that causes a match is not performed before the data breakpoint exception
is taken. When the exception occurs, the DAR is set to the address of the data access that
caused the breakpoint, and DSISR[9] is set. The address of the instruction associated with
the matching data access is saved in SRR0. Upon execution of an
rfi
instruction, the
instruction addressed in SRR0 is retired, and all results are committed to the destination
address in memory.
1.3.8.3
Breakpoint Signaling
The breakpoint signaling provided on the G2_LE core allows observability of breakpoint
matches external to the core. The core_iabr
,
core_iabr2, core_dabr, and core_dabr2
breakpoint signals are asserted for at least one bus clock cycle when the respective
breakpoint occurs.
When DBCR and IBCR are configured for an OR combinational signal type, the
breakpoint signals core_iabr, core_iabr2 and core_dabr, core_dabr2 reflect their
respective breakpoints.
When the DBCR and IBCR are configured for AND combinational signal type, only
the core_iabr2 and core_dabr2
breakpoint signals are asserted after the AND
condition is met (both instruction breakpoints occurred or both data breakpoints
occurred).
The breakpoint signaling conditions are described in Chapter 11, “Debug Features.”
1.3.8.4
Other Debug Resources
In addition to the four breakpoint registers and two breakpoint control registers, other
internal register values control and observe the effects of breakpoint conditions. Table 1-5
shows these registers and their bits.
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