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XMEM for Rabbit BL4S200 and xalloc / root2xmem / xmem2root

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I have a production application that requires persistent storage. I have been using the bbram keyword, but my needs have changed and I wish to use xmem instead.

Presently, I have about a 16K struct that I am saving in persistent storage. I am putting in a "fencepost" (0xcaa93004 as the first and last 32-bit long's) so I can tell if the area is "sane" or has been clobbered.

I used TN248 as a starting point. So here is the problem. For my production software, the memory gets clobbered whenever I power-cycle the Rabbit. If I use bbram keyword, it works fine, but if I use xmem if does not.

So I wrote a test program, reading and writing the exact same struct.

I use xalloc (type = XALLOC_BB), xmem2root and root2xmem for allocating, reading and writing the data respectively.

The test program works PERFECTLY even after a power cycle. The production software does not.

Furthermore, when I check the pointer value returned from xalloc, the test program reports 0xc8b0, but the production software reports 0x59012.

However, these addresses ARE CONSISTENT through multiple power-cycles of the Rabbit board, so I'm thinking - who cares, as long as the address is consistent through multiple reboots.

I'm trying to make XMEM work reliably first. I have to then perform some refactoring as the area in persistent storage need to grow to about 32k, after which I can no longer shadow the entire block to processor RAM. I have to use the far_memcpy to move sections of it at a time for my production application.

Questions:
1. Why is the memory getting over-written in one case and not in the other?
2. Instead of using xalloc to reserve the xmem and then shadow it to root memory? Is there a better way to just have this data fixed in xmem?

I can attach the test program but since it works, I'm not sure there is much point in that.

Thanks in advance
asked Nov 15, 2013 in Rabbit Software by caarecengi New to the Community (0 points)
edited Nov 15, 2013 by caarecengi

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