Suddenly out of ROM

SkeeterHawk · Joined: 16 Oct 2010 Posts: 56 Location: Florissant, CO

Hello programming Friends!

I had a weird issue that I can definitely work around, but I wanted to see if someone had an opinion as to what happened. I am using a PIC18F57Q84 with compiler version 5.114. I am loading an EEPROM with entries for a look-up table, so this is just a lot of monotonous code. I compiled about 7000 lines of code, and it said that I had used 52% of my available ROM. I wrote 2000 more lines, and the compiler "choked". Here is what it said

Jerson · Joined: 31 Jul 2009 Posts: 130 Location: Bombay, India

Usually, what this means is the code / a part of it doest not fit into a memory segment. The way you can resolve this is to look into making certain parts SEPARATE (keyword)

Ttelmah · Joined: 11 Mar 2010 Posts: 19914

Yes. Jerson is spot on.
The point is you don't have one single 'lump' of program memory, it is
divided into pages. Your code doing this job it being built as one 'lump',
so when you went over 50%, it will no longer fit into the page. Previously,
at 52%, you probably had several other bits occupying perhaps just a few
percent of this, that the compiler could put into another page, so you had this in one page and then just under 50% in the second. Now this single lump
will no longer fit.
You need to split it and it can then fit....

temtronic · Posted: Tue Aug 05, 2025 9:52 am

you may be able to break down the HUGE lookup table into 'segment fitting' chunks.
IE if it's a graphic database, consider segments for 'upper case', 'lower case' 'special symbols'. You'll need to add a simple 'test' to goto the correct table of course.

SkeeterHawk · Joined: 16 Oct 2010 Posts: 56 Location: Florissant, CO

Thank you all for the input on this. I suspected that something like this is the issue, but I am a little surprised that I have never run into this before. So if I was writing this in assembly, would it just stop assembling the code unless I put a new Origin statement in the middle of it somewhere? Obviously this is a function of the hardware and would carry over into assembly as well, so I am just curious.

Thanks again for all of your input!! Very Happy

_________________
Life is too short to only write code in assembly...

dyeatman · Joined: 06 Sep 2003 Posts: 1964 Location: Norman, OK

If you go to PIC24 or DsPIC the problem goes away...
_________________
Google and Forum Search are some of your best tools!!!!

SkeeterHawk · Joined: 16 Oct 2010 Posts: 56 Location: Florissant, CO