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diff --git a/cpu_supplement/preface.rst b/cpu_supplement/preface.rst new file mode 100644 index 0000000..b9c6102 --- /dev/null +++ b/cpu_supplement/preface.rst @@ -0,0 +1,54 @@ +======= +Preface +======= + + +The Real Time Executive for Multiprocessor Systems +(RTEMS) is designed to be portable across multiple processor +architectures. However, the nature of real-time systems makes +it essential that the application designer understand certain +processor dependent implementation details. These processor +dependencies include calling convention, board support package +issues, interrupt processing, exact RTEMS memory requirements, +performance data, header files, and the assembly language +interface to the executive. + +Each architecture represents a CPU family and usually there are +a wide variety of CPU models within it. These models share a +common Instruction Set Architecture (ISA) which often varies +based upon some well-defined rules. There are often +multiple implementations of the ISA and these may be from +one or multiple vendors. + +On top of variations in the ISA, there may also be variations +which occur when a CPU core implementation is combined with +a set of peripherals to form a system on chip. For example, +there are many ARM CPU models from numerous semiconductor +vendors and a wide variety of peripherals. But at the +ISA level, they share a common compatibility. + +RTEMS depends upon this core similarity across the CPU models +and leverages that to minimize the source code that is specific +to any particular CPU core implementation or CPU model. + +This manual is separate and distinct from the RTEMS Porting +Guide. That manual is a guide on porting RTEMS to a new +architecture. This manual is focused on the more mundane +CPU architecture specific issues that may impact +application development. For example, if you need to write +a subroutine in assembly language, it is critical to understand +the calling conventions for the target architecture. + +The first chapter in this manual describes these issues +in general terms. In a sense, it is posing the questions +one should be aware may need to be answered and understood +when porting an RTEMS application to a new architecture. +Each subsequent chapter gives the answers to those questions +for a particular CPU architecture. + +.. COMMENT: COPYRIGHT (c) 1988-2002. + +.. COMMENT: On-Line Applications Research Corporation (OAR). + +.. COMMENT: All rights reserved. + |