| ??? 08/02/07 04:51 Read: times |
#142612 - Flash uncertainty Responding to: ???'s previous message |
In support of Jan, I can confirm that, when not erased/programmed properly, flash can easily be in an indeterminate state.
So if power fails during erase of page 0, you might find that any of the bits that were zero previously, may or not be erased to ones. In fact, bits can become "half erased" and return different values at different times, depending on environmental factors (like temperature). So I don't think there is any way to safely erase the boot page under these circumstances. Erik Malund said:
my ISRs need be pretty fast and an additional ljmp may be a problem What would you say if someone came to this forum and said: "I am going to rely on the undefined properties of a device because I think I can't afford one extra LJMP in an ISR". I don't like to put words in your mouth, but from what I have seen, I expect you would say: (a) Don't ever base your design on undefined properties of a device, and (b) If you are so close to the line that you can't afford one extra LJMP somewhere, then use a faster device. |
| Topic | Author | Date |
| an attempt at a failsave bootloader | 01/01/70 00:00 | |
| do you REALLY need that 1kB? | 01/01/70 00:00 | |
| I'll have to think on that one - excellent idea | 01/01/70 00:00 | |
| Flash uncertainty | 01/01/70 00:00 | |
| I did not consider | 01/01/70 00:00 | |
| extra jump and enough power | 01/01/70 00:00 | |
| extra junp | 01/01/70 00:00 | |
| no magic idea... | 01/01/70 00:00 | |
| maths problem | 01/01/70 00:00 | |
| I am absolutely sure... | 01/01/70 00:00 | |
| the penalty of an extra ljmp... | 01/01/70 00:00 | |
| Dont ReWrite Page 0 | 01/01/70 00:00 | |
not a PC ... | 01/01/70 00:00 |