On Sun, 12 Feb 2006 14:52:21 +0100, you wrote:

>I was looking at some PIC pinouts for a new product. I would like to
>accomodate 16F877(A), 18F452 and 18F4520. To my horros I saw that the
>I/O pins of the 18F452 and 18F4520 are different: 18F452 has a full port
>D, 18F4520 has a full port A! Yet the migration document does not seem
>to mention this at all. 
>
>Can anyone with 18F452->18F4520 migration experience comment on this?

I think you have mis-read the datasheet.
The basic port pinout is the same. 
The differences are : 
MCLR can be RE3
RA4 is a normal pin, not open-drain
More pins can be analogue inputs. 

Upgrading an existing 452 design, the main difference is the ADC ADCON register configuration. 

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