#separate and out of ROM

Greg · Joined: 24 Dec 2003 Posts: 7

Hi,
I am programming a PIC16f877 using the PCW PCM C compiler.
I have been getting the error message "out of ROM a segement of the program is too large" i looked in the .sta file and noticed that rom useage is "ROM used: 1835 (90%)" and all my functions are in page 0 and the main function seems to be too big, inside my main function i have relativly little code but i call alot of other functions so i added the #SEPARATE directive before the decleration and definition of some of the bigger functions that i call and continued to call the functions in the same way. this seemed to have no effect. the compiler still complains about being out of ROM. IT appears that all the fucntiosn are still within page 0 after doign this and the rom usage for the main function hasnt changed.
Can anyone give me some tips as to what i may be doing wrong?
Thanks in advance
Greg

Greg · Joined: 24 Dec 2003 Posts: 7

Hi,
I suppose my real problem is understanding how the compiler and the program memory pages work. The pic16f877 has: "8K x 14
words of FLASH program memory" and the compiler is saying that having used 1718 words it is 84% full, what does this mean?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I don't have PCW, so I don't have a .STA file to look at.
However, if this statement that you've posted,
"ROM used: 1718 (84%)" is the same thing that is shown
at the top of the .LST file, then something is wrong.
Can you look at the top of your .LST file and tell me
if it has the statement above ?

The implication of that statement is that your PIC has only
2048 words of ROM, total. But a 16F877 has 8192 words.

Based on your previous post concerning the EEPROM, I have
to ask you this question: Does your version of PCW actually
support the 16F877, or did you substitute another PIC for it in
the #include file statement, in the hope that it would work ?

Also, what version of PCW do you have ?

Greg · Joined: 24 Dec 2003 Posts: 7

Well at the top of the lst file i have this:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

OK. Finally we get the whole story. Smile

You're using the Demo version.
CCS PCM C Compiler, Version 3.177d, 15332

It has a 2k limit on code size, per the CCS Demo page,
in the section on "About the Demo":
http://www.ccsinfo.com/demo.shtml

Greg · Joined: 24 Dec 2003 Posts: 7

Well, i told you i was probably doing something silly ;)
Thanks for all your help!!
Greg

gramya8712 · Guest

Hi even i have exactly the same problem of "out of ROM memory"
can any one give suggestions how to correct it and also how to divide the program into different pages??

thanks

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

This thread gives an example of breaking up one large function into
two smaller functions to solve the "out of rom" problem:
http://www.ccsinfo.com/forum/viewtopic.php?t=26793&start=8