Out of Rom, A segment or the program is too large...

edhaslam · Joined: 15 Jul 2005 Posts: 89 Location: UK

Hi all,

I'm converting some code from an old F877A project and running it on a an 18F452. I'm getting the "Out of Rom, A segement or the program is too large" error message. If I comment out the following org statement that I use for storing info in EEPROM, then everything is fine:

newguy · Joined: 24 Jun 2004 Posts: 1907

I suspect the problem lies with where you're trying to put that data with the #org.

In the 18F's, the EEPROM starts at address 0xf00000, as opposed to 0x2100 for the 16F's. If you search for "#rom 0xf00000" you'll find lots of posts dealing with the same issue. If you relocate your version and date information into the pic's data EEPROM, then you'll probably avoid your "out of rom" error.

Hope this helps.

edhaslam · Joined: 15 Jul 2005 Posts: 89 Location: UK

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

edhaslam · Joined: 15 Jul 2005 Posts: 89 Location: UK

Many thanks PCM, that was very useful indeed. I'll test the new settings and perhaps move them to the end of the ROM.

What is the benefit of doing this? Does it matter where they reside in ROM?

Ed

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Well, you were the one who wanted to do this. I was just supplying
the technical information so you could do it. Mr. Green

Let's speculate on reasons for locating the version strings in a
specific location:

1. Assuming that you're using MPLAB to program the PICs, it would
allow the user to look in the Program Memory window and easily
locate the version information, and thereby confirm that the proper
version is being programmed.

2. If you were doing a bootloader, and the bootloader code was
located in a specific area of the ROM, and you wanted to put the
bootloader version information there as well, then you might do this.

3. Perhaps you want to assist the compiler in partitioning functions and
data in ROM, and so you decide to "help" the compiler by putting
the version information in some out-of-the-way location like the
end of ROM memory.

I assume you have some reason for doing it. It's up to you to decide
if you need to do it.

Guest · Posted: Wed Nov 30, 2005 8:23 am

Ttelmah · Guest

Basically. you increase the 'segmentation' of the memory, requiring the compiler to not only optimise to deal with the processor limitations, but also to work out how to cope with this immovable block. It is a bit like adding a codicil to a book. If you add it at the end, the book can remain unchanged, as can the indexes etc.. However it you insisted on adding it in the middle, all the indexes have to change, and if the book is sectional, you may end up spliting a 'chapter', making it impossible to fit in either part.
Now ignoring this, seperately, there is the question of how much space is actually needed for a declaration. If you declare a 'const', then the compiler includes the code to access the constant, _in_ the declaration. So what you declare will not fit in the space you are allowing. This was the point made by PCM programmer, together with the point that an ORG like this, only places the next declaration at the specified address, so two declarations are needed.
If instead you make a ROM declaration, only the declared data is generated. So, if you had declared your data as:

sonicdeejay · Joined: 20 Dec 2005 Posts: 112

In my LST file... i can't find... #org

to change...

#org 0x07F0, 0x07FF

ROM 0x7F0 = {"v0.01",
"24/11/05"}