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