VR4102 datasheet(118/701 Pages) NEC

118 / 701 page

CHAPTER 5 MEMORY MANAGEMENT SYSTEM

118

Figure 5-1. Virtual-to-Physical Address Translation

Virtual address

The offset is then added to the PFN

passing through the TLB.

If there is a match, the page frame

number (PFN) representing the high-

order bits of the physical address is

output from the TLB.

The virtual page number (VPN) in the

virtual address (VA) is compared with

the VPN in the TLB.

TLB

entry

Physical address

TLB

ASID

Offset

VPN

Offset

PFN

ASID

VPN

5.2.1 Virtual-to-Physical Address Translation

Converting a virtual address to a physical address begins by comparing the virtual address from the processor

with the virtual addresses in the TLB; there is a match when the virtual page number (VPN) of the address is the

same as the VPN field of the entry, and either:

— the Global (G) bit of the TLB entry is set to 1, or

— the ASID field of the virtual address is the same as the ASID field of the TLB entry.

This match is referred to as a TLB hit. If there is no match, a TLB Mismatch exception is taken by the processor

and software is allowed to refill the TLB from a page table of virtual/physical addresses in memory.

If there is a virtual address match in the TLB, the physical address is output from the TLB and concatenated with

the offset, which represents an address within the page frame space. The offset does not pass through the TLB.

Instead, the low-order bits of the virtual address are output without being translated. See descriptions about the

virtual address space for details. For details about the physical address, see 5.4.9 Virtual-to-Physical Address

Translation.

The next two sections describe the 32-bit and 64-bit mode address translations.

VR4102 Datasheet(PDF) 118 Page - NEC