Fujitsu FR81S User Manual
CHAPTER 3: CPU
10. Memory Protection Function (MPU)
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : CPU
FUJITSU SEMICONDUCTOR CONFIDENTIAL
25
10.1. Overview
This section explains the overview of memory protection function (MPU) of the CPU.
This architecture supports a memory protection function. The memory protection function is a function that
monitors access to a specified area and generates an exception on prohibited access. However, protection
specified on system registers is ignored.
⋅
Eight protection areas can be specified that are shared by instructions and data
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The protection area with the highest priority is area 0, with the priority decreasing for areas 1, 2, 3, etc.
(The areas can overlap)
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Areas are specified by a page address and a page size
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Page size: Can be specified in units of 2
n
bytes from 16 bytes
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Page address: Misaligned addresses also supported
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The following access privileges are controlled using privilege mode and user mode
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Instruction fetch: Enabled/ Disabled
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Data Read:
Enabled/ Disabled
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Data Write:
Enabled/ Disabled
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Attributes are specified for each area
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Buffer:
Enabled/ Disabled
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The access rights and attributes of undefined areas are controlled as a default area
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Protection violation exceptions occur when a protection violation occurs
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The register for the memory protection function can only be accessed in a privilege mode as system
registers
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Data access error notification function
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I/O area (00000000
H
to 0000FFFF
H
) is fixed buffer disabled
MB91520 Series
MN705-00010-1v0-E
122