questions for those who have experience with #org

[truevenik]

Hi. I'm using PCM v3.163 and PIC16F877. I need to reduce code size and I've noticed that about 1/10 of the assembly code deals with the A.3 and A.4 bits. I haven't yet looked at how good the compiler is at distributing functions among ROM pages, but I'm guessing I can make some improvements. So I want to start manually mapping functions to ROM pages using #org.

1)are there any known compiler bugs associated with #org?

2)how do I avoid interfering with things like the interrupt handler and all that other code the compiler places in page0?

3)I don't know of an easy way to get the size of my functions, so I don't want to explicitly locate functions - I just want to specify which page they should be in. If I understood the manual correctly, I do this using
#org 0x00, 0x800
function1_in_page0() {}
#org 0x00
function2_in_page0()
will this work?

4)when is it better to use
#org start,end DEFAULT
#org DEFAULT

5)will the compiler put out an error message if I put too many functions in a segment?

6)using #org as above doesn't change the way the compiler alocates RAM variables right?


Thanks for any help
-Ben

[PCM programmer]

1)are there any known compiler bugs associated with #org?
I don't think so.

2)how do I avoid interfering with things like the interrupt handler
and all that other code the compiler places in page0?
The compiler won't let you do it. You'll get an "invalid ORG range" error.

3)I don't know of an easy way to get the size of my functions, so I don't
want to explicitly locate functions - I just want to specify which page they
should be in. If I understood the manual correctly, I do this using
#org 0x00, 0x800
function1_in_page0() {}
#org 0x00
function2_in_page0()
will this work?

It won't work because the reset and interrupt code goes at locations 0
and 4, respectively, for the 16F877. The interrupt dispatcher could be
100 ROM words long, depending on how many interrupt service routines
you have. So you'll have to set the starting address of the first
segment to a number greater than 0. Use 0x100 to be perfectly sure
it will compile. Or, try smaller values until it compiles without error.

Also, your proposed segment end address of 0x800 is not corrrect.
The end address of the 1st ROM page is 0x7FF.


4)when is it better to use
#org start,end DEFAULT
#org DEFAULT
The default statement will move the internal routines, such as "DIV8"
into the segment specified with the Default keyword. But that's only
done if the code that invokes the internal library routines occurs AFTER
the initial Default statement.

5)will the compiler put out an error message if I put too many functions in a segment?
Definitely.

6)using #org as above doesn't change the way the compiler allocates RAM variables right?
I don't know.


Here is a sample program. I suggest you experiment with it,
and look at the .LST file and the Program Memory window in
MPLAB, to see where the compiler is putting the code.

[Haplo]

Just a quick note; it seems there were a few issues associated with #org and they have been fixed in version 3.189 (released today), as per CCS' changelog.

[truevenik]

Hi, lets say I have a function g(int x). Is there a way to make two copies of it and put one in ROM page1, and another in page2 ?
Also, does anyone know of a way to use #org on a function, keep the function's prototype (so that functions can be arranged in any order in a source file), and not have to make the function #seperate (so that stack depth is still checked by the compiler) ?

thanks
-Ben