2 ms·
Yeah, as you suggest by your "slightly safer" parenthetical, the mechanical write protection on most SD cards is just a suggestion that the card reader is free
by jnbiche 12y ago
Yeah, as you suggest by your "slightly safer" parenthetical, the mechanical write protection on most SD cards is just a suggestion that the card reader is free to ignore (though obviously most don't).
It's actually specified in the SD spec [1], which says on p. 38 that the mechanical protect switch is "Host responsibility only" and that the "The position of the write protect switch is unknown to the internal circuitry of the card."
1. https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf https://www.sdcard.org/downloads/pls/simplified_specs/part1_... [pdf file]
- tehwalrus 12y agoI did read that somewhere, but I'd forgotten.. Good catch! Hardware write protection is harder to find than you think..
- semi-extrinsic 12y agoThe popular CHDK custom firmware for Canon compact cameras subverts the write-protect tab on the SD card to be a CHDK on/off switch. So it's widely known that software may ignore this switch.
- TeMPOraL 12y agoI keep wondering why create a feature only to not implement it? What was the reasoning behind this soft write protection mechanism?