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#1 2014-11-26 09:25:41
- iceman
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- Registered: 2013-04-25
- Posts: 9,506
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ARM - Available memory
How is the memory used in the arm? I got a 512kb ARM but I always get the feeling only the 64kb SRAM is used. Can someone shed a light in this matter?
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#2 2014-11-26 10:52:47
- piwi
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- Registered: 2013-06-04
- Posts: 704
Re: ARM - Available memory
No, both memory types are used:
512K (or 256K with smaller versions of the ARM) is the Flash Memory which is used for the bootloader, (most of) the executable code and the FPGA configuration data. The content of this memory survives a power on reset.
64K is the SRAM which used for the executable code which is declared "RAMFUNC", all the variables, dynamically allocated memory, and the stack. Content of this memory is lost when power is lost.
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#3 2014-11-26 12:56:15
- iceman
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Re: ARM - Available memory
aha, thanks Piwi.
But how do I know how much memory I used from the 256/512 kb ?
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#4 2014-11-26 13:51:13
- piwi
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- Registered: 2013-06-04
- Posts: 704
Re: ARM - Available memory
The linker creates a file armsrc/obj/fullimage.map which contains information on memory consumption. With the latest commit I find (among some negligible segments)
.fpgaimage: 0x1497e
.text: 0x135b8
.rodata: 0x2703
.data: 0x2918
.bss: 0xa0bcThe first three go into the Flash Memory and add up to 173625 Bytes. Note: half of this space is used for the (meanwhile two separate LF and HF) FPGA images. The rest is executable code and readonly data (constants).
The latter two go into the SRAM and add up to 51668 Bytes. This are initialized variables and RAMFUNCs and unitialized data (global and static local).
Which leaves us with 13868 Bytes for the heap (dynamic memory allocation) and the stack (including automatic local variables).
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#5 2014-11-26 14:19:07
- iceman
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- Registered: 2013-04-25
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Re: ARM - Available memory
And now my is question, how can I move the BigBuffer to my abundant 512kb instead of the 64kb sram?
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#6 2014-11-26 15:09:00
- piwi
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- Registered: 2013-06-04
- Posts: 704
Re: ARM - Available memory
Make it readonly by declaring it const and initialize its contents at compile time already. 
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