source: rtems/doc/supplements/sh/memmodel.t @ 8f30e3e

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Last change on this file since 8f30e3e was 8f30e3e, checked in by Joel Sherrill <joel.sherrill@…>, on 11/25/98 at 16:25:12

First Cut at Hitachi SH.

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1@c
2@c  COPYRIGHT (c) 1988-1998.
3@c  On-Line Applications Research Corporation (OAR).
4@c  All rights reserved.
5@c
6@c  $Id$
7@c
8
9@chapter Memory Model
10
11@section Introduction
12
13A processor may support any combination of memory
14models ranging from pure physical addressing to complex demand
15paged virtual memory systems.  RTEMS supports a flat memory
16model which ranges contiguously over the processor's allowable
17address space.  RTEMS does not support segmentation or virtual
18memory of any kind.  The appropriate memory model for RTEMS
19provided by the targeted processor and related characteristics
20of that model are described in this chapter.
21
22@section Flat Memory Model
23
24The XXX family supports a flat 32-bit address
25space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4
26gigabytes).  Each address is represented by a 32-bit value and
27is byte addressable.  The address may be used to reference a
28single byte, word (2-bytes), or long word (4 bytes).  Memory
29accesses within this address space are performed in big endian
30fashion by the processors in this family.
31
32Some of the XXX family members such as the
33XXX, XXX, and XXX support virtual memory and
34segmentation.  The XXX requires external hardware support
35such as the XXX Paged Memory Management Unit coprocessor
36which is typically used to perform address translations for
37these systems.  RTEMS does not support virtual memory or
38segmentation on any of the XXX family members.
39
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