Bit Kernel Mode Segments - NEC uPD98502 User Manual

Address Bit
Value KSU
A31 = 0
A(31:29) = 100
A(31:29) = 101
A(31:29) = 110
A(31:29) = 111
(1) kuseg (32-bit kernel mode, user space)
When KX = 0 in the Status register, and the most-significant bit of the virtual address space is 0, the kuseg virtual
address space is selected; it is the current 2-Gbyte (2
The virtual address is extended with the contents of the 8-bit ASID field to form a unique virtual address.
If the ERL bit of the Status register is 1, the user address space is assigned 2 Gbytes (2
mapping and becomes unmapped (with virtual addresses being used as physical addresses) and uncached so
that the cache error handler can use it. This allows the Cache Error exception code to operate uncached using r0
as a base register.
(2) kseg0 (32-bit kernel mode, kernel space 0)
When KX = 0 in the Status register and the most-significant three bits of the virtual address space are 100, the
kseg0 virtual address space is selected; it is the current 512-Mbyte (2
References to kseg0 are not mapped through TLB; the physical address selected is defined by subtracting 8000
0000H from the virtual address.
The K0 field of the Config register controls cacheability (see Section 2.5 Exception Processing).
(3) kseg1 (32-bit kernel mode, kernel space 1)
When KX = 0 in the Status register and the most-significant three bits of the virtual address space are 101, the
kseg1 virtual address space is selected; it is the current 512-Mbyte (2
References to kseg1 are not mapped through TLB; the physical address selected is defined by subtracting A000
0000H from the virtual address.
Caches are disabled for accesses to these addresses, and main memory (or memory-mapped I/O device
registers) is accessed directly.
(4) ksseg (32-bit kernel mode, supervisor space)
When KX = 0 in the Status register and the most-significant three bits of the virtual address space are 110, the
ksseg virtual address space is selected; it is the current 512-Mbyte (2
address is extended with the contents of the 8-bit ASID field to form a unique virtual address.
112
CHAPTER 2 V
Table 2-29. 32-bit Kernel Mode Segments
Status Register Bit Value
EXL ERL KX
KSU = 00 0
or
EXL = 1
or
0
ERL = 1
0
0
0
Preliminary User's Manual S15543EJ1V0UM
4120A
R
Segment Virtual
Name Address
kuseg 0000_0000H
to
7FFF_FFFFH
kseg0 8000_0000H
to
9FFF_FFFFH
kseg1 A000_0000H
to
BFFF_FFFFH
ksseg C000_0000H
to
DFFF_FFFFH
kseg3 E000_0000H
to
FFFF_FFFFH
31
-byte) user address space.
29
-byte) physical space.
29
-byte) physical space.
29
-byte) virtual address space. The virtual
Physical Size
Address
TLB map 2 Gbytes
31
(2 bytes)
0000_0000H 512 Mbytes
29
to
(2 bytes)
1FFF_FFFFH
0000_0000H 512 Mbytes
29
to
(2 bytes)
1FFF_FFFFH
TLB map 512 Mbytes
29
(2 bytes)
TLB map 512 Mbytes
29
(2 bytes)
31
bytes) without TLB