Whether the code changes, it depends. In principle, yes, bcus the 12C509
has the (obsolete) 12-bit kernel, i. e.
- no IT
- only 2 level of subroutine calls allowed (instead of 8)
- simpler instruction set (slightly)
- of course: no internal EEPROM
- less RAM I guess

And a personal experience: no PICs dead in my hands except a windowed
12C509, and w/o any obvious reason. Since I have some fear against it. If
you must save REALLY try 16C54B (has the same disadvantages but maybe less
sensitive).

Imre


On Thu, 21 May 1998, PHXSYS wrote:

> Hi
>
> I have some simple code I wrote and debugged for a 16F84. It only uses 4 pins.
> I was wondering what changes I would have to make to use a 12C509?
>
> This chip is much cheaper and I don't need the 16F84's 13 i/o lines or the
> flash. I see the eprom specs for the 12C509 is 1Kx12 vs 1Kx14 for the 16F84.
> Does that change the way code is written?
>
> Jon
>
>