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Basics: C programming for ARM - AHB transfers

joewu joewu
Offline over 6 years ago
Note: This was originally posted on 18th September 2007 at http://forums.arm.com

Hello,
Would someone please help me about the next basic things?
I have programed microcontrollers in the past but now I need to work with ARM processors and need some basic pieces to connect the puzzle.
I wil write a C/C++ code for ARM966 but I don't know what to do in the code to communicate to an AHB peripheral. It should be memory mapped but I don't know at what location and if I need to do the memory initalisation at the start of the code or I can read it from somewhere - I have not been able so far to find a clear document about that.
Also, I expect that is enough for me to write to that location in the memory and to read from it and the compiler 'armcc' will take care of generating AHB transaction data that will go to ARM AHB interface ports. I am right or there are specific C functions for AHB transfers in both directions?
I expect to have a library of the C functions that I can use in the code but also somehow I couldn't find the place where it is explained.
I have been digging over RealView 3.0 (Unix) directories in the search for that and I see several header files (like rt_heap.h, rt_memory.h and so on) but I don't have any single C project example where I can see their usage.
I would really apreciate if someone can give me some examples or point me to a location where I can read about that.
The same questions go for the tightly coupled memory (TCM) - where is it in the memory map and so on.
Any help is appreciated.
Thank you very much,
joewu
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  • 0 Offline over 6 years ago
    Note: This was originally posted on 19th September 2007 at http://forums.arm.com

    Thank you again, it is nice of you to try to help me with this.
    I understand what you are saying but still don't see when the memory map is configured and who decides at what location AHB peripheral will be mapped and how I can know that now in the early development phases. Do I have to do it in some initialization stage afterward and how? Is there C API for that (not SystemC, just C or C++)?
    Then, let's say I found somehow that location and have written something to it. Now I want to read the answer from that particular peripheral. I would expect to have a separate address for AHB HRDATA[31:0] bus - is my assumption correct here or it is also taken care of automatically?
    These are all the simple basic questions and I beleive after a little example it would all click in place for me.
    It seems to me I also need to spend some time in adding and configuring an AHB peripheral but it is very distant in the flow and I need to do some programming now.
    Many thanks...
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  • 0 Offline over 6 years ago
    Note: This was originally posted on 19th September 2007 at http://forums.arm.com

    Thank you again, it is nice of you to try to help me with this.
    I understand what you are saying but still don't see when the memory map is configured and who decides at what location AHB peripheral will be mapped and how I can know that now in the early development phases. Do I have to do it in some initialization stage afterward and how? Is there C API for that (not SystemC, just C or C++)?
    Then, let's say I found somehow that location and have written something to it. Now I want to read the answer from that particular peripheral. I would expect to have a separate address for AHB HRDATA[31:0] bus - is my assumption correct here or it is also taken care of automatically?
    These are all the simple basic questions and I beleive after a little example it would all click in place for me.
    It seems to me I also need to spend some time in adding and configuring an AHB peripheral but it is very distant in the flow and I need to do some programming now.
    Many thanks...
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