where is the problem ?

[Calamar]

using the following code without initialize index
will hung-up the MC(16f877a) only some times, when
local_funtion() is called at firsttime after power-on, any idea ?


// gloabal declaration

const int cursorX[] = {16,13,11,10,8,7,6,5,4,3,16,9};
int index;

//

loacal_funtion(){

int xPostion;
xPosition = cursorX[index];

}
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)

[rwyoung]

Then initialize RAM at reset so your index variable will be zero.

Or declare it as

[Mark]

[Calamar]

You both are righ I must should initialize index, verify bounds
and so on, but why the MC get lost ?perhaps mark did it
but I didnt get it
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)

[Calamar]

You both are righ I must should initialize index, verify bounds
and so on, but why the MC get lost ?perhaps mark did it
but I didnt get it
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)

[Ttelmah]

The 'key', is in how constant arrays are stored on the 16 family chips. On these, there are no instructions to access the program memory. So how do you store the numbers?. The answer, is the instruction 'RETLW', which returns to the program that called it, with the byte held in the rest of the word holding the instruction. So to access a constant array, what is done, is a subroutine is called, which then adds the index to the current program counter address, and jumps 'into' the array, where there is a RETLW instruction to return the required byte.
If your index is outside the range of the array, you will be jumping to another location in memory, with a return address on the stack, and never return.
CCS, do no bounds checking, because it costs time. Hence you have to either ensure that the value will always be legitimate, or implement your own bounds check.

Best Wishes

[Calamar]

It`s, clear now, thank you and mark
_________________
Best Regards
Daniel H. Sagarra
La Plata (Argentina)