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Mapping in C

 
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Mapping in C
boschow
14 May, 2007 - 01:03 AM
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Hi,

is mapping used for linking two program's variables. I mean if i have program A with variable a1, and program B with variable a1. How do i know that the change of variable in program A also occurs in program B and the change of variable in program B also occurs in program A. Is this what is mapping used for ? If yes, what is the easyest way to "map" variables? What is the moust efficient way to write this tipe of program?

Thanks for your time and help
Best Regards,
BoSCHoW
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Trogdor
RE: Mapping In C
15 May, 2007 - 05:34 AM
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As far as i understand what you are trying to say the answer is no.
But you might want to elaborate and rephrase your question, and perhaps illustrate it a bit.
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boschow
RE: Mapping In C
16 May, 2007 - 12:05 AM
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Well lets say that i am programming a microprocessor and i also want to make a program for parametrisation wich can communicate with this chip through a serial communication protocol. This program would have access to all the parameters located in the microprocessor. My question is, how is this done and how do i know that for example the address 1 in the application is the same as in the microprocessor "if i write 50 in address 1 of the application, how do i know that address 1 in the microcontroller wil change to 50" ?

This post has been edited by boschow: 16 May, 2007 - 12:13 AM
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Trogdor
RE: Mapping In C
16 May, 2007 - 09:22 AM
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So you are aiming on a kind of shared memory.
A program on the microcontroller will use it, and an external program.
Is that correct?

The only way (as far as i know) to get exact controll of where a program stores variabeles is to program in assembler. But i might be wrong, there can be compiler constructs for it.

I programmed an embedded system a long time ago. Then I had the same problem more or less, but solved it differently: the program running on the embedded system also handeled the communication with the outside world.
When that outside world asked for stored data (some timestamps + numbers of personell badges) it simply took the data out of the in-memory datastructure (array of structs) and pumped it back through the serialport.
Worked flawlessly.
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