From ae68ff085724dd35d60151bd153e80b8b0776873 Mon Sep 17 00:00:00 2001 From: Joel Sherrill Date: Tue, 27 May 1997 12:40:11 +0000 Subject: Initial revision --- doc/supplements/m68k/memmodel.t | 52 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 doc/supplements/m68k/memmodel.t (limited to 'doc/supplements/m68k/memmodel.t') diff --git a/doc/supplements/m68k/memmodel.t b/doc/supplements/m68k/memmodel.t new file mode 100644 index 0000000000..91ccf8010d --- /dev/null +++ b/doc/supplements/m68k/memmodel.t @@ -0,0 +1,52 @@ +@c +@c COPYRIGHT (c) 1988-1996. +@c On-Line Applications Research Corporation (OAR). +@c All rights reserved. +@c + +@ifinfo +@node Memory Model, Memory Model Introduction, Calling Conventions User-Provided Routines, Top +@end ifinfo +@chapter Memory Model +@ifinfo +@menu +* Memory Model Introduction:: +* Memory Model Flat Memory Model:: +@end menu +@end ifinfo + +@ifinfo +@node Memory Model Introduction, Memory Model Flat Memory Model, Memory Model, Memory Model +@end ifinfo +@section Introduction + +A processor may support any combination of memory +models ranging from pure physical addressing to complex demand +paged virtual memory systems. RTEMS supports a flat memory +model which ranges contiguously over the processor's allowable +address space. RTEMS does not support segmentation or virtual +memory of any kind. The appropriate memory model for RTEMS +provided by the targeted processor and related characteristics +of that model are described in this chapter. + +@ifinfo +@node Memory Model Flat Memory Model, Interrupt Processing, Memory Model Introduction, Memory Model +@end ifinfo +@section Flat Memory Model + +The MC68xxx family supports a flat 32-bit address +space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4 +gigabytes). Each address is represented by a 32-bit value and +is byte addressable. The address may be used to reference a +single byte, word (2-bytes), or long word (4 bytes). Memory +accesses within this address space are performed in big endian +fashion by the processors in this family. + +Some of the MC68xxx family members such as the +MC68020, MC68030, and MC68040 support virtual memory and +segmentation. The MC68020 requires external hardware support +such as the MC68851 Paged Memory Management Unit coprocessor +which is typically used to perform address translations for +these systems. RTEMS does not support virtual memory or +segmentation on any of the MC68xxx family members. + -- cgit v1.2.3