Product : ISaGRAF V3
Date : 5-March-1996
File : Ppk8bit.Porting ISaGRAF under an 8 bit processor.htm
Subject : Porting ISaGRAF under an 8 bit processor
Keywords: Porting - IDK - 8 bit
There is no problem making a porting of ISaGRAF under a poor (8 or
16 bit processor) if you have an ANSI C compiler for this processor.
You just have to focus on the limits of such an implementation:
- Some of the ISaGRAF advanced features (ethernet communication,
multitasking) are conditioned by the power of the host system. On a
poor operating system, or if no system exist, the porting will be
limited to a single task (one main loop) implementation.
- All integer calculations under ISaGRAF operate 32 bit values. This
may lead to very poor performances for applications with a large
part of analog variables and operations.
- Normally, some high level capabilities such as floating point and
message strings are not reasonable on a little processor. They lead
to a huge kernel code and low response times.
- Finally, even if the memory is not limited, be care of the memory
model supported by the C compiler. For example: if data addressing
is segmented with a 16 bit offset, the maximum size of an
application cannot exceed 64 Kbytes.
Most of all, remember that using ISaGRAF, comparing to C or assembly
code programming, you add a certain amount of software layers which
grants opening, easy portability and programming in very high level
languages. Obviously this consumes processor time.
To summarise, porting ISaGRAF under a poor micro-processor is
totally feasible, but must be applied to small or medium ISaGRAF
applications. (handling mainly booleans, and with a limited number
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