Nios® II Processor Reference Guide

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

3.7.7.13. TLB Permission Violation

TLB permission violation exceptions are implemented only in Nios® II processors that include the MMU. When a TLB entry is found matching the VPN (optionally extended by a process identifier), but the permissions do not allow the access to complete, a TLB permission violation exception is generated.

There are three kinds of TLB permission violation exceptions:

  • TLB permission violation (execute)—Any instruction fetch can cause this exception.
  • TLB permission violation (read)—Any load instruction can cause this exception.
  • TLB permission violation (write)—Any store instruction can cause this exception.

The general exception handler can inspect the exception.CAUSE field to determine which permissions were violated.

Note: The data cache management instructions (initd, initda, flushd, and flushda) ignore the TLB permissions and do not generate TLB permission violation exceptions.

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