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Weird problem using external memory driver

 
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JimNewbie
Guest
Weird problem using external memory driver
PostPosted: Sun Mar 29, 2009 5:22 am     Reply with quote
hi,
I came across this problem and I hope that someone would help me to understand it.

Here is the problematic code:
Code:
#define PIC188F88722_EXT_MEM_START 0x20000L 
typedef struct
{
  uint32   start_addr;
  uint32   end_addr;
  uint8     num_block;
} my_test_ext_mem_stype;

my_test_ext_mem_stype my_test_ext_mem;

// This function is having problem
void test_mem_function (void)
{
  uint16  temp_read, temp_write, index;

  my_test_ext_mem.start_addr = PIC188F88722_EXT_MEM_START ;

  for (index = 0; index < 1000; index++)
  {
    temp_write = index + 33;
    write_external_memory(my_test_ext_mem.start_addr ,&temp_write,2);
    read_external_memory(my_test_ext_mem.start_addr ,&temp_read,2);
   
    if (temp_write != temp_read)
    {
      temp_read = temp_write;  <<<----- It will hit here alot
    }
  }
}


Also the same function, If I modify it like this, my test memory will be passed.
Code:

void test_mem_function (void)
{
  uint16  temp_read, temp_write, index;
  uint32  start_address;
  start_address = PIC188F88722_EXT_MEM_START ;

  for (index = 0; index < 1000; index++)
  {
    temp_write = index + 33;
    write_external_memory(start_address ,&temp_write,2);
    read_external_memory(start_address  ,&temp_read,2);
   
    if (temp_write != temp_read)
    {
      temp_read = temp_write;  <<<----- won't hit here.
    }
  }
}


or like this, still work
Code:
void test_mem_function (void)
{
  uint16  temp_read, temp_write, index;
 
  for (index = 0; index < 1000; index++)
  {
    temp_write = index + 33;
    write_external_memory(PIC188F88722_EXT_MEM_START ,&temp_write,2);
    read_external_memory(PIC188F88722_EXT_MEM_START ,&temp_read,2);
   
    if (temp_write != temp_read)
    {
      temp_read = temp_write;  <<<----- won't hit here.
    }
  }
}


or even this also works
Code:
void test_mem_function (void)
{
  uint16  temp_read, temp_write, index;

  my_test_ext_mem.start_addr = (PIC188F88722_EXT_MEM_START - 2) ;

  for (index = 0; index < 1000; index++)
  {
    temp_write = index + 33;
    write_external_memory(my_test_ext_mem.start_addr + 2 ,&temp_write,2);
    read_external_memory(my_test_ext_mem.start_addr + 2,&temp_read,2);
   
    if (temp_write != temp_read)
    {
      temp_read = temp_write;  <<<----- won't hit here. Good to go
    }
  }
}

Please help me to explain this kind of weird behavior.
Thank you
JimNewbie
Guest
PostPosted: Sun Mar 29, 2009 5:31 am     Reply with quote
btw, I was using CCS 4.087 and I just update the new version 4.090. Both have the same problem.

It is PIC 18F8722.
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