arrays - no memory space

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

I am using PIC16F877A, compiler version 3.190.
I have got quite few arrays in my program, and that causes not enough memory space in RAM.
When I use #locate, the program counter becomes noughty and does not follow the program addresses sequence, and the code does not work then.
It seems like if I use const arrays instead, I can't use pointers
So, my code then doesn't work.
What is the solution for that?
Thank you
_________________
Alex

Ttelmah · Guest

John P · Joined: 17 Sep 2003 Posts: 331

You can use the #ROM directive to put stuff in program ROM, and as a bonus when you do that the data is a 14 bit word. I've found there's a limit to how much data the compiler lets you store that way, though. If you need more, you can make an addition to your program's HEX file before burning the program in--tedious to do, but works OK.

But if it's RAM you need, pure and simple, then you need a bigger processor, or an off-board RAM.

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

treitmey · Joined: 23 Jan 2004 Posts: 1094 Location: Appleton,WI USA

If your board isn't finished you could add an fram.

It is nearly and fast as ram.
I2C,.. so its easy to hook up.
drivers are writen for it.

I use the ramtron fm24c04 FRAM.

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

Thank you guys
_________________
Alex

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

Kieran · Joined: 28 Nov 2003 Posts: 39 Location: Essex UK

Have a look at the manufacturers site

http://www.ramtron.com

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

newguy · Joined: 24 Jun 2004 Posts: 1907

Go for it. Yes, you'll spend some time porting to the 18-family, but all the code you've written is still valid.

Plus, buying the PCH compiler will allow you to target a lot of new chips.

I learned a long time ago that if I try to scrimp and save on tools, that I'll just end up paying for it later (either for the tool I should have bought in the first place, or in time lost). Spending a little money on a great development tool (PCH) is money well spent, in my opinion.

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

newguy · Joined: 24 Jun 2004 Posts: 1907

Whoops. I'm confused.

I thought that you were using the CCS compiler to write your application. There are 3 different versions of the CCS compiler: one for the 12-series (PCB), one for the 16-series (PCM), and another for the 18-series (PCH).

Since you mentioned that you were writing code for a 16F-something PIC, I assumed that you owned the CCS PCM compiler. If this was true, then all you'd need to do in order to upgrade to the 18-series PICs would be to buy CCS's PCH upgrade.

Sorry. Porting code written for another compiler will be a little painful, but I still think that CCS is a great product.

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

newguy · Joined: 24 Jun 2004 Posts: 1907

The only difference is that the PCH compiler allows you to target the 18-series PICs. Everything else is identical. I think that CCS charges $75 for the upgrade. It is WELL worth it. Plus, you get 30 days of free upgrades with the purchase. These upgrades are for all of their compilers (PCB, PCM, and PCH). So for $75, you gain the ability to write code for the 18 family, and you get your present compiler (PCM) upgraded to the latest version.

I know that I'll get jumped on for that, so I'll just save everyone the opportunity: I know that the latest version can be buggy. You can also download the "last known good" version with your 30 day download rights.

alexz · Joined: 17 Sep 2004 Posts: 133 Location: UK

Another question:
What is preferable PCH or C18?
And what are advantages and disadvantages?
_________________
Alex