migrating from 16f877a to 18f452

[TIMT]

Hi there,

I'm in the process of converting an assembly code program to C with CCS. My current program is using a 16f877a which is rapidly getting filled up using C - Mostly because I'm doing things in C which I wouldn't have attempted to do in assembler! My question is, the larger (more memory) 18f452 seems to be pin for pin compatible with the 16f877a, can I just take my C code for the 16f877a, create a project for a 18f452 and pull it into this project (making changes to the header files etc..) ? or is it a bit more difficult than that?

I've only been using CCS for four weeks so go easy on me if this is an obvious question!
Regards Tim.
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Tim

[newguy]

What you want to do should work. If I'm not mistaken, I believe that the 452 has an extra timer, timer 3, that the 877A doesn't have. You'll need to make sure that it powers up disabled; if not, you'll need to add code to disable it.

The only thing you need to watch out for is if you directly access any of the special function registers. For instance, I always put my buttons/keypad on port b, and I usually directly access port b in my code. For the 16 chips, port b is at address 6 (I think), but for the 18 chips, it's at address 0xF81. Minor changes like that.

The only other area where you may see some odd behavior is with the watchdog. You set it up differently in the 18 series than you do with the 16's.

Hope this helps.

[Humberto]

[TIMT]

Thanks for your replies, doesn't look like it should be too difficult! I think the lcd driver handles the different port locations. I didn't know the 452 was being superceeded by the 4520 I had heard some people have had problems with it. Might still use it though to begin with as I have one on order. I'll keep an eye on the timer3 settings when I set up the project.
It'll be good having 32k(16k) of memory to play with instead of trying to cram everything into 8k! Regards...
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Tim