Copying structs from rom

[thomasj50]

Hi,
I have a large struct that I would like to place in prom (as a const) and be copied to a ram version at startup. I use an ordinary assignment for this:

typedef struct
{
... contents
} S;

S a;
S b;

...

a = b is ok, all variables in b gets copied to a, but if I change
S b;
to
const S b;

the assignment fails (i.e. no data is copied). Furthermore, this seems
to take a very long time to single step in the debugger, actually I have never had the patience to wait it out (minutes).

Anyone know anything about this ? I use version 4.014.
Best Regards,
Thomas Johansson

[PCM programmer]

I made the test program shown below, and it works OK with
PCH vs. 3.249. It displays the following output:

[thomasj50]

Hi,

Yes, it works all right with version 4.014 too. This is a much smaller example but it should make no difference. I will have to separate out the code to test it separate from the application.

Thomas J.

[thomasj50]

Try this change. It uses a pointer to the struct in ram, and fails as long as
the keyword const is in place, but works otherwise. My printout looks like this:

Before: 0 0 0 .
After: 0 22 3 ........,........a..@..3... .


typedef struct
{
int8 val1;
int8 val2;
int8 val3;
int8 buf[20];
}S;

const S a = {1,2,3, "Hello World"};

S b;
S* bp;

//====================================
void main()
{
b = 0;
printf("Before: %u %u %u %s \n\r", b.val1, b.val2, b.val3, b.buf);

bp = &b;
*bp = a;
printf("After: %u %u %u %s \n\r", b.val1, b.val2, b.val3, b.buf);

while(1);
}

[PCM programmer]

I can confirm that it doesn't work. I looked at the .LST file for both
your recent post and my post. In the non-pointer version, the compiler
generates code to do Table Reads (which reads from the Flash memory).
In the pointer version, it doesn't do that. It's attempting to use the FSR
register to copy from RAM to RAM. It's a bug. I can't immediately
think of a work-around for it. This was with PCH vs. 3.249.

[thomasj50]

Ok, thanks for the help with debugging this! I can work around it in my code, the ram struct is static so I can use it directly instead of going trough a pointer (the copy was in a subroutine, hence the pointer). Should I tell CCS about this or do they watch this list continously, do you think ?

Best Regards,
Thomas Johansson

[PCM programmer]

No, they don't watch this board. Send an email to CCS support.
Give them the compiler version number and a short (but complete)
test program that shows the problem. Also give them your user
reference number.