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-rw-r--r-- | doc/supplements/arm/memmodel.t | 38 |
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diff --git a/doc/supplements/arm/memmodel.t b/doc/supplements/arm/memmodel.t new file mode 100644 index 0000000000..bf543364c7 --- /dev/null +++ b/doc/supplements/arm/memmodel.t @@ -0,0 +1,38 @@ +@c +@c COPYRIGHT (c) 1988-2002. +@c On-Line Applications Research Corporation (OAR). +@c All rights reserved. +@c +@c $Id$ +@c + +@chapter Memory Model + +@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. + +@section Flat Memory Model + +Members of the ARM family newer than Version 3 support 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 the endian +mode that the processor is configured for. In general, ARM +processors are used in little endian mode. + +Some of the ARM family members such as the +920 and 720 include an MMU and thus support virtual memory and +segmentation. RTEMS does not support virtual memory or +segmentation on any of the ARM family members. + |