VR4102 datasheet(127/701 Pages) NEC

127 / 701 page

CHAPTER 5 MEMORY MANAGEMENT SYSTEM

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(4) xsseg (64-bit Supervisor mode, current supervisor space)

When SX = 1 in the Status register and bits 63 and 62 of the virtual address space are set to 01, the xsseg

virtual address space is selected; it covers 1 Tbyte (2

40 bytes) of the current supervisor virtual address space.

The virtual address is extended with the contents of the 8-bit ASID field to form a unique virtual address. This

mapped space begins at virtual address 0x4000 0000 0000 0000 and runs through 0x4000 00FF FFFF FFFF.

(5) csseg (64-bit Supervisor mode, separate supervisor space)

When SX = 1 in the Status register and bits 63 and 62 of the virtual address space are set to 11, the csseg

virtual address space is selected; it covers 512 Mbytes (2

29 bytes) of the separate supervisor virtual address

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

This mapped space begins at virtual address 0xFFFF FFFF C000 0000 and runs through 0xFFFF FFFF DFFF

FFFF.

5.2.7 Kernel-mode Virtual Addressing

If the Status register satisfies any of the following conditions, the processor runs in Kernel mode.

— KSU = 00

— EXL = 1

— ERL = 1

The addressing width in Kernel mode varies according to the state of the KX bit of the Status register, as follows:

— When KX = 0, 32-bit kernel space is selected.

— When KX = 1, 64-bit kernel space is selected.

The processor enters Kernel mode whenever an exception is detected and it remains in Kernel mode until an

exception return (ERET) instruction is executed and results in ERL and/or EXL = 0. The ERET instruction restores

the processor to the mode existing prior to the exception.

Kernel mode virtual address space is divided into regions differentiated by the high-order bits of the virtual

address, as shown in Figure 5-6. Table 5-3 lists the characteristics of the 32-bit Kernel mode segments, and Table

5-4 lists the characteristics of the 64-bit Kernel mode segments.

VR4102 데이터시트(PDF) 127 Page - NEC