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Rev. 5.00, 09/03, page 61 of 760
3.1.4 Register Configuration
A register that has an undefined initial value must be initialized by software. Table 3.1 shows the
configuration of the MMU control registers.
Table 3.1 Register Configuration
Name Abbreviation R/W Size
Initial
Value
*
1
Address
Page table entry register high PTEH R/W Longword Undefined H'FFFFFFF0
Page table entry register low PTEL R/W Longword Undefined H'FFFFFFF4
Translation table base register TTB R/W Longword Undefined H'FFFFFFF8
TLB exception address register TEA R/W Longword Undefined H'FFFFFFFC
MMU control register MMUCR R/W Longword
*
2
H'FFFFFFE0
Notes: 1. Initialized by a power-on reset or manual reset.
2. SV bit: undefined
Other bits: 0
3.2 Register Description
There are five registers for MMU processing. These registers are located in address space area P4
and can only be accessed from privileged mode by specifying the address.
1. The page table entry register high (PTEH) register residing at address H'FFFFFFF0, which
consists of a virtual page number (VPN) and ASID. The VPN set is the VPN of the virtual
address at which the exception is generated in case of an MMU exception or address error
exception. When the page size is 4 kbytes, the VPN is the upper 20 bits of the virtual address,
but in this case the upper 22 bits of the virtual address are set. The VPN can also be modified
by software. As the ASID, software sets the number of the currently executing process. The
VPN and ASID are recorded in the TLB by the LDTLB instruction.
2. The page table entry register low (PTEL) register residing at address H'FFFFFFF4, and used to
store the physical page number and page management information to be recorded in the TLB
by the LDTLB instruction. The contents of this register are only modified in response to a
software command. (Refer to section 3.4.3, MMU Instruction (LDTLB), and section 3.5,
MMU Exceptions.)
3. The translation table base register (TTB) residing at address H'FFFFFFF8, which points to the
base address of the current page table. The hardware does not set any value in TTB
automatically. TTB is available to software for general purposes.
4. The TLB exception address register (TEA) residing at address H'FFFFFFFC, which stores the
virtual address corresponding to a TLB or address error exception. This value remains valid
until the next exception or interrupt.