migrating from 16F886/7 to 18F ??

[asmboy]

assuming one is happy with the assorted peripheral and I/O capability of the 16f88x but wants
much program and user ram
( as can be hard in a 28 and 40 pin package - )

any suggestions on 18F ?

[Ttelmah]

Probably the 2520 (for the 28pin device), and 4520 for the 4 pin device. Same basic peripherals, double the ROM, and about five times the RAM. Generally cheaper than the older chips. You can also gain extra I/O pins, with the MCLR pin programmable as an input, and if your application does not require really high accuracy, you can use the internal oscillator, to give two more pins here. Clocks over 50% faster. Be prepared for 18 code to be slightly larger for things like interrupt handlers, but smaller for things like multiply.

Best Wishes

[asmboy]

thanks for your generous help

the microchip site SAYS migration is EZ - but in half an hour of poking around - i never could FIND that pesky interactive migration tool they talked about ...
have you ??

either way MUCH appreciated

[dyeatman]

Be careful of the pitfall that gets a lot of folks... Many of the register addresses are different so, if things don't work correctly, be sure to double check them...

You might get lucky and all the ones you use are in the header file and no additional changes will be required.

Also, if you get a "not defined" message for a constant during the compile check that the spelling hasn't changed in the .H file.

Dave

[Ttelmah]

The migration tool, is for Microchip assembler code, not CCS.
Migration with CCS, varies according to how your code is written.
If you use 'pure CCS' code (no assembler, and no direct register accesses), then all that needs to be done, is to change the header references, get the 18 compiler version (PCH, rather than PCM) update the fuses (generally the 18 chips add a few new fuses), compile, and the code will probably run (99% probability).
If you use direct register accesses, these will need to be updated.
If you use assembler, this will need to be re-written (though things like the automatic register addressing of the CCS compiler, make the changes small).
If the chip adds extra peripherals, these will need to be disabled.
I have a program that has versions running in both the 18F452, and the 16F887. The same source code is used for both, with about a dozen lines, selected by a #ifdef, changing the fuses required. Otherwise, it runs 'as is'.

Best Wishes

[asmallri]

[Ttelmah]

A bit 'roundabouts and swings'. I have had more errata problems still showing their faces on these versions of the chips. Both derivatives have had a lot of problems, but the 2520 has been working OK, for the last couple of years, while the 2620, still shows some real surprises.
I do still consider the 2520, slightly more reliable.
I does depend 'massively' on how much more memory is needed. These give 4* the ROM, versus the 2520, giving 2*.

Best Wishes