
MOTOROLA
Chapter 2. Register Model
2-17
Register Set
Table 2-9 describes the bit settings for the DCMP and ICMP registers.
2.1.2.6
Primary and Secondary Hash Address Registers
(HASH1 and HASH2)
HASH1 and HASH2, shown in Figure 2-7, contain the physical addresses of the primary
and secondary PTEGs for the access that caused the TLB miss exception. For convenience,
the G2 core automatically constructs the full physical address by routing SDR1 bits 0–6
into HASH1 and HASH2 and clearing the lower 6 bits. These read-only registers are
constructed from the DMISS or IMISS contents (the register choice is determined by which
miss most recently occurred).
Figure 2-7. HASH1 and HASH2 Registers
Table 2-10 describes the bit settings of the HASH1 and HASH2 registers.
2.1.2.7
Required Physical Address Register (RPA)
During a page table search operation, the software must load the RPA, shown in Figure 2-8,
with the second word of the correct PTE. When the
tlbld
or
tlbli
instruction is executed, the
RPA and 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 accessible to the software.
Table 2-9. DCMP and ICMP Bit Settings
Bits
Name
Description
0
V
Valid bit. Set by the processor on a TLB miss exception.
1–24
VSID
Virtual segment ID. Copied from VSID field of corresponding segment register.
25
—
Reserved, should be cleared.
26–31
API
Abbreviated page index. Copied from API of effective address.
Table 2-10. HASH1 and HASH2 Bit Settings
Bits
Name
Description
0–6
HTABORG
Copy of the upper 7 bits of the HTABORG field from SDR1
7–25
Hashed page address
Address bits 7–25 of the PTEG to be searched
26–31
—
Reserved
0
6
7
25
26
31
HTABORG
Hashed Page Address
0 0 0 0 0 0
F
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