At 10:40 AM 2/8/2006 -0500, you wrote:
>I'm about to migrate a project from a 452 to the 4520.  While comparing the
>datasheets I noticed that RA4 on the 452 is shown as being "open drain when
>configured as output", but on the 4520 it is never mentioned that RA4 is
>also open drain.

Because it's not. See DS39647A "PIC18F452 -> PIC18F4520 Migration" Note 3
on page 7.

>  In my board design I have the anode of an LED connected to
>RA4 with the cathode connected to +5V via a 1K resistor,

?? That doesn't make much sense to me. If you are shunting the LED
with RA4 to turn it off, then you'll have to make some changes. If you
have the open-drain output conducting to turn the LED "on" , then no
changes should be necessary.

>so I will have to
>reverse it and change my code, very easy to do but I was under the
>impression that the 4520 was pin-compatible with the 452.  Is this not the
>case?

Not exactly the same, obviously. But RA4 is still RA4, not, say OSC1.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist