NXP Semiconductors PXN2020, Reference Manual, Page: 441 / 1376

PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 18-1
Chapter 18
Memory Protection Unit (MPU)
18.1 Introduction
The memory protection unit (MPU) provides hardware access control for all memory references generated
in a device. Using pre-programmed region descriptors that define memory spaces and their associated
access rights, the MPU concurrently monitors all system bus transactions and evaluates the
appropriateness of each transfer. Memory references with sufficient access control rights are allowed to
complete, but references that are not mapped to any region descriptor or have insufficient rights are
terminated with a protection error response.
The MPU implements a set of program-visible region descriptors that monitor all system bus addresses.
The result is a hardware structure with a two-dimensional connection matrix, where the region descriptors
represent one dimension and the individual system bus addresses and attributes are the second dimension.
NOTE
The MPU module is not implemented on the PXN20.
18.1.1 Block Diagram
A simplified block diagram illustrates how the MPU block is connected to the four AXBS-lite MPU ports
and the shared port splitter (see
Figure 18-1 ).