TMPR4956C datasheet(106/286 Pages) TOSHIBA

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Chapter 4 Memory Management System

4-12

Table 4.2.3 32-bit Kernel Mode Segments

Status Register

Is One Of These Values

Address

Bit Values

KSU

EXL

ERL

Segment

Name

Address Range

Segment Size

A[31] = 0

Kuseg

0x0000 0000

through

0x7FFF FFFF

2 Gbytes

31 bytes)

A[31:29] = 1002

Kseg0

0x8000 0000

through

0x9FFF FFFF

512 Mbytes

29 bytes)

A[31:29] = 1012

Kseg1

0xA000 0000

through

0xBFFF FFFF

512 Mbytes

29 bytes)

A[31:29] = 1102

Ksseg

0xC000 0000

through

0xDFFF FFFF

512 Mbytes

29 bytes)

Kseg3

0xE000 0000

through

0xFFFF FFFF

512 Mbytes-4 Mbytes

29 bytes)

A[31:29] = 1112

KSU = 002

EXL = 1

ERL = 1

Reserved

(Note)

0xFF00 0000

through

0xFF3F FFFF

4 Mbytes

Note : 0xff00_0000 through 0xff3f_ffff in 32-bit mode is reserved (unmapped, uncached) for use by

registers in the Debug Support Unit and the processor’s peripherals.

32-bit Kernel Mode, User Space (kuseg)

In Kernel mode, when KX

= 0 in the Status register, and the most-significant bit of the virtual address,

A31, is cleared, the 32-bit kuseg virtual address space is selected; it covers the full 2

31 bytes (2 Gbytes) of

the current user address space. The virtual address is extended with the contents of the 8-bit ASID field to

form a unique virtual address. When ERL = 1 in the Status register, the user address region becomes a 2

bytes unmapped (that is, mapped directly to physical addresses) uncached address space.

32-bit Kernel Mode, Kernel Space 0 (kseg0)

In Kernel mode, when KX = 0 in the Status register and the most-significant three bits of the virtual

address are 1002, 32-bit kseg0 virtual address space is selected; it is the 2

29 bytes (512 Mbytes) kernel

physical space. References to kseg0 are not mapped through the TLB; the physical address selected is

defined by subtracting 0x8000 0000 from the virtual address. The K0 field of the Config register,

described in this chapter, controls cacheability and coherency.

32-bit Kernel Mode, Kernel Space 1 (kseg1)

In Kernel mode, when KX = 0 in the Status register and the most-significant three bits of the 32-bit

virtual address are 1012, 32-bit kseg1 virtual address space is selected; it is the 2

29 bytes (512 Mbytes)

kernel physical space. References to kseg1 are not mapped through the TLB; the physical address selected

is defined by subtracting 0xA000 0000 from the virtual address. Caches are disabled for accesses to these

addresses, and physical memory (or memory-mapped I/O device registers) are accessed directly.

32-bit Kernel Mode, Supervisor Space (ksseg)

In Kernel mode, when KX = 0 in the Status register and the most-significant three bits of the 32-bit

virtual address are 1102, the ksseg virtual address space is selected; it is the current 2

29 bytes (512 Mbytes)

supervisor virtual space. The virtual address is extended with the contents of the 8-bit ASID field to form

a unique virtual address.

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