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| p.3 #18 · Canon EF 40mm f/2.8 STM Lens Firmware v1.2.0 update! |
Turning off the camera doesn't help against card removal during write either. The camera won't turn itself off until the writing is finished. In either case, just wait until the write LED has gone off.
The LED is the only safe guide to when the card can be removed without damage.
Yeah I've never turned the camera off. I just wait for the light to go off and then switch the card (like just about everyone else I know). I remember some of the early DSLRs actually had a little alarm that would beep when you opened the door to inform you that you should not pull the card while it's still writing.
If Datalight DOS is anything like windows (versus Linux), devices like CF cards are mounted as removable meaning writes take priority and the write cache will always be emptied as soon as possible.
Probably what happened here is that the firmware update was only tested in an older camera that didn't store, update, or have access to the battery data. For some reason, the two interfere.
BTW in the embedded world, generally, "off" is not really off. In most cases, flipping the power switch to 'off' merely puts the device to sleep, putting the SRAM and micro in a low-power sleep mode where state is retained. This way you have instant-on capability versus, say, the original Digital Rebel (300D) where after turning the camera on, you could not shoot a photo for about a second or two (because the firmware had to boot up).
So when it locked up in the firmware update, and refused to turn off even if you flipped the switch, that's why. The firmware is hung and nonresponsive to input. Why Canon didn't bother with a hardware watchdog, I don't know. Pulling the battery will power down the micro so you get a reboot when you put it back in. The only state retained when the battery is pulled is battery-backup RAM, flash, and NVRAM.
If you don't believe this, turn your camera off. Then turn it back on, and see how quickly you can take a photo: instantly (as long as your DSLR isn't really old). Now leave the switch on, but open the battery door (with most of the current Canons, this alone cuts the battery power. You don't actually have to eject the battery). Close the battery door, and try to take a photo right away. You can't, because the firmware is booting. It takes around 1-2 seconds before you can take the photo.