PXD20RM Datasheet, PDF (125/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Chapter 4
Safety
4.1 Register Protection
4.1.1 Introduction
4.1.1.1 Overview
The Register Protection module offers a mechanism to protect defined memory-mapped address locations
in a module under protection from being written. The address locations that can be protected are
module-specific.
The protection module is located between the module under protection and the PBRIDGE. This is shown
in Figure 4-1.
PBRIDGE
peripheral enable
Protection Module
Access allowed?
peripheral
enable
supervisor access /
address / access size
write data
Lock
Registers
Other control signals
UAA
GCR
HLB
Module
under
Protection
Figure 4-1. Register Protection Block Diagram
4.1.1.2 Features
The Register Protection includes these distinctive features:
• Restrict write accesses for the module under protection to supervisor mode only
• Lock registers for first 6 KB of memory-mapped address space
• Address mirror automatically sets corresponding lock bit
PXD20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
4-1
Preliminary—Subject to Change Without Notice