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

of variables).


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