
MOTOROLA
Chapter 2. Register Model
2-21
Register Set
SPR311 in supervisor mode. The present memory base address for the system memory map
is stored in this register. It is important to ensure that the present value of the base offset is
current in the system memory.
2.1.2.14 Instruction Address Breakpoint Registers (IABR and IABR2)
The IABR, shown in Figure 2-14, controls the instruction address breakpoint exception. In
the G2_LE core, an additional address breakpoint register (IABR2) is implemented.
IABR[CEA] holds an effective address to which each instruction’s address is compared.
The exception is enabled by setting IABR[BE]. The exception is taken when there is an
instruction address breakpoint match on the next instruction to complete. The instruction
tagged with the match cannot complete before the breakpoint exception is taken. The
address of the instruction which matches the breakpoint condition is stored in SRR0. The
tagged instruction is completed and retired on return from the exception (
rfi
or
rfci
). The
results are then committed to the destination registers and address.
Note that if the IABR/IABR2 register values are set to any exception vector, an
unrecoverable processor state will occur.
Figure 2-14. Instruction Address Breakpoint Registers (IABR and IABR2)
The bits in the IABR and IABR2 are defined in Table 2-13. For more information about the
instruction breakpoint exception, see Section 5.5.16, “Instruction Address Breakpoint
Exception (0x01300).”
2.1.2.14.1 Instruction Address Breakpoint Control Registers
(IBCR)—G2_LE Only
The IBCR, shown in Figure 2-15, is a supervisor-level register with SPR309 on the G2_LE
core, which is accessible only by using an
mtspr
or
mfspr
instruction. The IBCR controls
the compare and match type conditions for IABR and IABR2. Note that IABR and IABR2
must be enabled before the effects of IBCR are realized.
Table 2-13. Instruction Address Breakpoint Register (IABR and IABR2) Bit Settings
Bits
Name
Description
0–29
CEA
Compare effective address. Word address to be compared.
30
BE
Breakpoint enable. IABR (or IABR2) enabled. Setting this bit enables the IABR exception.
31
—
Reserved
0
29 30 31
CEA
BE 0
Reserved
F
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.