
MOTOROLA
Chapter 2. Programming Model
2-11
2.1.2.5 Required Physical Address Register (RPA)
The RPA register is shown in Figure 2-7. During a page table search operation, the software
must load the RPA with the second word of the correct PTE. When the
tlbld
or
tlbli
instruction is executed, the contents of the RPA register and the DMISS or IMISS register
are merged and loaded into the selected TLB entry. The referenced (R) bit is ignored when
the write occurs (no location exists in the TLB entry for this bit). The RPA register is read
and write to the software.
Figure 2-7. Required Physical Address Register (RPA)
Table 2-6 describes the bit settings of the RPA register.
2.1.2.6 Instruction Address Breakpoint Register (IABR)
The IABR, shown in Figure 2-8, controls the instruction address breakpoint exception.
IABR[CEA] holds an effective address to which each instruction is compared. The
exception is enabled by setting bit 30 of IABR. The exception is taken when there is an
instruction address breakpoint match on the next instruction to complete. The instruction
tagged with the match will not be completed before the breakpoint exception is taken.
Figure 2-8. Instruction Address Breakpoint Register (IABR)
Table 2-6. RPA Bit Settings
Bits
Name
Description
0–19
RPN
Physical page number from PTE
20–22
—
Reserved
23
R
Referenced bit from PTE
24
C
Changed bit from PTE
25–28
WIMG
Memory/cache access attribute bits
29
—
Reserved
30–31
PP
Page protection bits from PTE
0
19 20
22
23 24 25
28 29 30 31
Reserved
RPN
R
C
WIMG
PP
0 0 0
0
0
29 30 31
Reserved
CEA
IE 0