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'16F876 -> 18F Series: Any porting issues?'
2002\10\02@155714 by Matt Heck

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Hi folks,

We're about to port some code we run on a PIC16F876 to an 18F series
part.  All the code is in assembly, and we HAVE been using MPLAB to
do most of the work, although we wouldn't mind switching...

Are there any "gotchas" we should know about running 16F code on an
18F part, or porting?  We don't expect it to be a completely drop-
in replacement, of course, but if there's anything particularily
weird, I'd sure appreciate a heads-up!

Thanks,
  Matt

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2002\10\02@162425 by Dr Martin Hill

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Hi,
 I have done this with one of our products, from a 16F876 to a 18F252,
there no real issues with it, I set the bank access pointer to bank one and
then just used bank one and the access bank which gave me all the variables
I needed.  I then went through all of the code adding either ,A or ,1 in the
relevant places for the variable locations, removed all the references to
PCLATH,3 and PCLATH,4 put in some BZ and BNZ instructions to shorted the
code slightly, changed the maths routines to incorporate the built in 8x8
multiply, and moved the interrupt locations as there are two interrupt
addresses with different priorities.
 You will find if you are using an include file for your eeprom data that
when you put that in MPLAB, the compiled file is lacking the  configuration
data, at least it was with version 5.5.  I had to add it in manually before
programming the parts.  The only gotcha I found was the multiplexing of
CCP2.

 Hope that helps.

Regards,

Martin


{Original Message removed}

2002\10\02@171555 by Matt Heck

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Thanks very much, Martin!  I'll post here if we get any suprises.  Our code
inclues a bootloader with write-to-self routines for both FLASH and EEPROM;
it'll be interesting to see how those port.  I love being able to have a
pin-for-pin, drop-in replacement for a part we outgrew, that turns out to
have a ton of major improvements.

I just wish there was an 18F part with more than 256K of EEPROM in a 28-SOIC!

Cheers,
  Matt Heck
  Crystal Engineering Corporation
  http://www.crystalengineering.net
  "Pressure is Our Business!"



{Original Message removed}

2002\10\02@172220 by Dr Martin Hill

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The bootloader routines are different.  I wrote completely new routines for
the ported version, forgot to mention that.  You will also need to remove
any references to changing STATUS,RP3 and RP4 for switching memory banks.
The code protection is much improved, that's worth checking up on as well.

Martin

{Original Message removed}

2002\10\02@173436 by Matt Heck

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Yes, we suspected that might be the case.  Thanks for the heads-up!

-----Original Message-----
From: Dr Martin Hill [.....mhillKILLspamspam@spam@RACE-TECHNOLOGY.COM]
Sent: Wednesday, October 02, 2002 2:21 PM
To: PICLISTspamKILLspamMITVMA.MIT.EDU
Subject: Re: 16F876 -> 18F Series: Any porting issues?


The bootloader routines are different.  I wrote completely new routines for
the ported version, forgot to mention that.  You will also need to remove
any references to changing STATUS,RP3 and RP4 for switching memory banks.
The code protection is much improved, that's worth checking up on as well.

Martin

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2002\10\03@104314 by Mike Mansheim

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> We're about to port some code we run on a PIC16F876 to an 18F series
> part.  All the code is in assembly, and we HAVE been using MPLAB to
> do most of the work, although we wouldn't mind switching...

> Are there any "gotchas" we should know about running 16F code on an
> 18F part, or porting?

The watchdog is set up differently.

Also, Microchip's AN716 might be worth a look.  It's not the exact
chips, but it covers the family change:  "Migrating designs from
PIC16C74A/74B to PIC18C442".

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2002\10\03@110408 by Michael Simpson

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If you use jump tables those will all have to be recoded.

The bit shift commands will have to be converted.

Your Register access will have to be modified.

All code dealing with code pages will have to be modified

Things to watch out for.......

Multi level interupts......   They just dont work that well.  Stick to
single priority interupts and you will be fine.


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