On Fri, 2005-09-23 at 09:01 -0400, Jon Ringle wrote: > On Friday 23 September 2005 08:09 am, Neundorf, Alexander wrote: > > 5. after the image is written, set the valid_flag of the fis directory > > which will become active to 0xa5a5. In order to do this, the flash block > > doesn't have to be erased, since the transition from 0xfdfd to 0xa5a5 only > > sets some bits to 0. > > I didn't know this property of flash. Is this a universal property of NOR > flash?
Yes. Erase operations reset all the bits to one. Programming can only change a one to a zero. This can be done on a bit by bit basis, thus you can update a block by changing some bits to zeroes without having to erase it. -- ------------------------------------------------------------ Gary Thomas | Consulting for the MLB Associates | Embedded world ------------------------------------------------------------
