Nios® II Processor Reference Guide

ID 683836
Date 10/22/2020
Public
Document Table of Contents

3.2.5. TLB Lookups

A TLB lookup attempts to convert a virtual address (VADDR) to a physical address (PADDR).

TLB Lookup Algorithm for Instruction Fetches


if (VPN match && (G == 1 || PID match)) 
   if (X == 1)
      PADDR = concat(PFN, VADDR[11:0])
   else take TLB permission violation exception
else
   if (EH bit of status register == 1)
      take double TLB miss exception
   else
      take fast TLB miss exception

TLB Lookup Algorithm for Data Access Operations


if (VPN match && (G == 1 || PID match))
   if ((load && R == 1) || (store && W == 1) || flushda)
      PADDR = concatenate(PFN, VADDR[11:0])
   else
      take TLB permission violation exception
else
   if (EH bit of status register == 1)
      take double TLB miss exception
   else
      take fast TLB miss exception

Refer to “Instruction-Related Exceptions” for information about TLB exceptions.

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