Feature: Memory
Safeguarding boot code and other
critical data with NOR Flash By Ken Lin, Deputy Director of Flash Memory Technical Marketing and Application Engineering, Winbond Electronics Corporation
S
PI NOR Flash is the electronics design engineer’s favourite memory type for low- density, high-reliability storage of application
code and data in embedded systems with storage requirements to 512Mbits. To facilitate broad adoption across
the industry, NOR Flash memory technology follows certain standards, for instance governing the serial interface to a host microcontroller or SoC. One of these standard features is the way NOR Flash allows the system designer to configure protection of stored data. Protection may be applied to a specific fraction of the entire memory array in
which mission-critical data is stored: most often this is boot code, since if this was impaired or lost, the entire system would be disabled. Protection ensures that the data in
protected blocks is not corrupted, for instance by noise, or mistakenly erased and overwritten by a faulty operation implemented by the host system. If an Erase or Program command specifies a memory region that contains a protected block, this command will be ignored. In other words, protected blocks are tagged as read-only memory. The way this standard approach
to data protection was implemented many years ago in NOR Flash has more recently, however, begun to constrain
designers’ flexibility in their use of the higher-density memory devices available today. This has prompted Winbond to introduce new, proprietary extensions to the standard protection functions, to give more control over block size and operation of the protection function.
Increase in protected block sizes When the data-protection function was created many years ago, NOR Flash memory densities were much smaller than today. At that time, just three Block Protection (BP) bits in the Flash IC’s status register were enough to specify the portion of the total memory array to be protected. On a Winbond NOR Flash memory device’s datasheet, these status
www.electronicsworld.co.uk November/December 2020 43
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
