Problem with PIC16F630 and debug

[Fabri]

Hi Everybody,

I have a problem in debug of PIC16F630 and MPLAB.

This is the first part of listing:

[Fabri]

I study about and I have a correction about,

In programming mode by ICD2 at 0x3ff there is a ADDLW 0xff only in simulation there is RETLW 0x00.

What is the meaning of line 4 call 0x3ff ?

Regards,

[Fabri]

Does anybody help me about?

I can't realize if the problem is in compiler, with call to 0x3FF, or MPLAB.

Have you got any ideas ?

Thanks for support

[Ttelmah]

The chips come from the factory, with a RETLW instrruction at address 0x3FF. This returns the calibration constant, that has to be put into 'OSCCAL', to calibrate the internal oscillator. The compiler, if you use the internal oscillator, will automatically insert the code to call this address, and then put the returned vaue into the calibration register.
The programmer should have an option to automatically preserve the contents of this location. Hence when you program the chip 'ADDLW 0x0', does not get put at this location, what happens is that the programmer reads the value at this location, and then writes the whole code, with this value included. In some programmers, there is a 'tick box' option to save the calibration constant.
For simulation, simply put a dummy RETLW at this point. In use, provided your programmer is set to save the calibration value, this will not cause a problem.

Best Wishes

[Fabri]

Hi,

I understand about but I can't realize how put in 0x3ff an RETLW 0.

Do you suggest me the way in C ?

Rergards,

[Ttelmah]

#ROM 0x3FF = { 0x3400 }

Beware though, to remove this before compiling to upload into the real chip, or you may overwrite the real calibration value.

Best Wishes

[Fabri]

Thanks for help, now the debug work right.

Bye..