Register Model
e200z3 Power Architecture Core Reference Manual, Rev. 2
2-34
Freescale Semiconductor
2.12
Debug Registers
This section describes software-accessible debug registers for use by special debug tools and debug
software, not by general application code. Software access to these registers is conditioned by the external
debug mode control bit (DBCR0[EDM]), which can be set by the hardware debug port. If DBCR0[EDM]
is set, software is prevented from modifying debug register values. Execution of an mtspr instruction
targeting a debug register does not cause modifications to occur. In addition, since the external debugger
hardware may be manipulating debug register values, the state of these registers is not guaranteed to be
consistent if read by software with an mfspr instruction other than DBCR0[EDM].
2.12.1
Debug Address and Value Registers
Instruction address compare registers IAC1–IAC4 hold instruction addresses for comparison. In addition,
IAC2 and IAC4 hold mask information for IAC1 and IAC3, respectively, when address bit match compare
modes are selected.
NOTE
During instruction address comparisons, the low-order two address bits of
the instruction address and the corresponding IAC register are ignored.
Data address compare registers DAC1 and DAC2 hold data access addresses for comparison. In addition,
DAC2 holds mask information for DAC1 when address bit match compare mode is selected.
2.12.1.1
Instruction Address Compare Registers (IAC1–IAC4)
IAC1–IAC4, shown in
, hold instruction addresses for comparison.
A debug event can be enabled when there is an attempt to execute an instruction from an address in one of
the following contexts:
•
In an IAC
•
Inside or outside a range specified by IAC1 and IAC2
•
Inside or outside a range specified by IAC3 and IAC4
•
To blocks of addresses specified by the combination of the IAC1 and IAC2
•
To blocks of addresses specified by the combination of the IAC3 and IAC4.
Because all instruction addresses must be word-aligned, the two low-order bits of the IACs are reserved
and do not participate in the comparison with the instruction address.
32
61 62 63
Field
Instruction address
—
Reset
All zeros
R/W
R/W
SPR
SPR 312 (IAC1); SPR 313 (IAC2); SPR 314 (IAC3); SPR 315 (IAC4)
Figure 2-29. Instruction Address Compare Registers (IAC1–IAC4)
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