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'[PIC]:18F452 Question'
2003\02\20@024257 by Jon M (Mike) Jones

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This isn't any big deal, just curious.

Since I don't have a programmer that reads the ID codes, I wrote
a short routine to read them. The results were;

0x3FFFFE: 0x25 (DEVID1)
0x3FFFFF: 0x04 (DEVID2)

The first (0x25) I interpret to read as: 18F452 Rev. 5 but what does DEVID2 indicate? The data sheet only says (that I could find) that it identifies the part number in DEVID1.

The part is stamped;
   18F452-I/P
   0239GG9

Does the 0x04 by any chance indicate the I/P part of the part number?

Assuming my method of reading the device ID codes and interpretation
of them is correct, I was a little surprised at the rev number. Since the B5 errata sheet only fairly recently appeared on the uChip website I would have thought that they would only in the last couple of months be shipping rev 5
parts, yet the date code on the part indicates week 39 of 2002. On the other hand, I guess they are under no obligation to keep the information on
their web site in sync with production.

Thanks for any response,

Mike Jones

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2003\02\20@034326 by Rob Hamerling

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face
Jon M (Mike) Jones wrote:

> Since I don't have a programmer that reads the ID codes, I wrote
> a short routine to read them. The results were;
>
> 0x3FFFFE: 0x25 (DEVID1)
> 0x3FFFFF: 0x04 (DEVID2)
>
> The first (0x25) I interpret to read as: 18F452 Rev. 5 but what does DEVID2
> indicate? The data sheet only says (that I could find) that it identifies the
> part number in DEVID1.

Device ID is a 16 bit field: DevID2/DevID1 of which the low oder 5 bits
are the revision code (for the 18Fxx2/xx8 family). Have a look at
DS39576A page 22.

Regards, Rob

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homepage: http://www.robh.nl/

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2003\02\20@081545 by Olin Lathrop

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>>
0x3FFFFE: 0x25 (DEVID1)
0x3FFFFF: 0x04 (DEVID2)

The first (0x25) I interpret to read as: 18F452 Rev. 5 but what does
DEVID2
indicate? The data sheet only says (that I could find) that it identifies
the
part number in DEVID1.
<<

This is incorrect.  See "Programming for PIC18Fxx2/Fxx8 Flash MCUs"
(DS39576A), page 22, section 5.2 "Device ID Word", and table 5-1 "Device
ID Value".

Both bytes are required to identify the particular chip.  Your DEVID1 in
this case only indicates 18F448 or 18F452 rev 5.  DEVID2 nails it down to
18F452.


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