is something taking a while to start up because of the cold? What sort of
oscillator are you using?

Perhaps it's not stable enough to write the first byte correctly, but has
"warmed up" enough to write the subsequent bytes...

By wamed up I mean started stable oscillations.

> -----Original Message-----
> From: Ben Jackson [SMTP:ben@BEN.COM]
> Sent: Monday, March 01, 2004 4:34 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC:] EEPROM write temperature dependence?
>
> I'm working on an 18F2320 device that I need to calibrate at several
> temperatures.  At the moment I'm just saving the raw cal data to a scratch
> area of EEPROM so I can read it back out and test it for sanity before
> manually adding it to tables.
>
> After several passes at about room temperature and 'fridge temperature'
> (around 40F, 4C) I tried it in the freezer (around 0F, -18C) and
> consistently the programming loop failed to write (left at 0xFF) the
> first EEPROM byte.
>
> -18C is well within the -40C minimum device temp.  The 5V power
> regulation is good.  All bytes after the first one write fine.
>
> Am I doing something wrong?  I can add a verify/rewrite loop but I'd
> like to understand why first.  Should I be setting WREN earlier?  Does
> that start the onboard charge pump?  Are the bytes that DO get written
> likely to be 'more fragile'?
>
> --
> Ben Jackson
> <ben@ben.com>
> http://www.ben.com/
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu