Nios® II Processor Reference Guide

ID 683836
Date 8/28/2023
Document Table of Contents The RD Flag

System software triggers a TLB read operation by setting tlbmisc.RD (with a wrctl instruction). A TLB read operation loads the following register fields with the contents of a TLB entry:
  • The tag portion of pteaddr.VPN
  • tlbmisc.PID
  • The tlbacc register

The TLB entry to be read is specified by the following values:

  • the line portion of pteaddr.VPN
  • tlbmisc.WAY

When system software changes the fields that specify the TLB entry, there is no immediate effect on pteaddr.VPN, tlbmisc.PID, or the tlbacc register. The registers retain their previous values until the next TLB read operation is initiated. For example, when the operating system sets pteaddr.VPN to a new value, the contents of tlbacc continues to reflect the previous TLB entry. tlbacc does not contain the new TLB entry until after an explicit TLB read.