Re: Boot Block and Uniform Block Flash Memory and Executin In Place(XIP)
- From: Juergen Beisert <jbeisert@xxxxxxxxxxxx>
- Date: Thu, 25 Oct 2007 08:51:46 +0200
Hi,
karthikbalaguru wrote:
My Queries are :-
1) But, What is the advantage of Top Boot Flash Memory and
What is the advantage of Bottom Boot Flash memory ?
Sometimes these special blocks are smaller than the others. This might be an
advantage, when you have to store some kind of variable information in it.
You waste less space in this case (the bootloader u-boot does so. Sometimes
you must waste 256kiB (one sector), but you only need 3kiB for the real
data).
2) Apart from protection to the Boot Block, what are the other
differences between these Boot Block based Flash memories
and Normal Flash Memories (Uniform Block Flash Memory)?
AFAIK no other difference.
3) Which is cost-effective (Boot Block based Flash or Normal
Flash ( Uniform Block Flash Memory) ) ?
Prepare your hardware and software to handle both types. Then you can always
buy the cheaper one.
4) Is the lifetime (Number of programmable / erase cycles)
of the Boot Block lesser than or equivalent to that of
the Normal Blocks (Application Code, User
Parameters and User Data)?
AFAIK no.
5) Can that Boot Block area used for other purporses w.r.t
security of the application ?
To store data the user can setup at runtime.
6) I understand that for systems with small amounts of memory,
XIP is very good that each instance of that program uses
system RAM, only for their stack, BSS, and data segments
while the shared text segment remains in Flash Memory.
But, Is there any specific Block dedicated for text segment
while performing XIP in either Boot Block Flash Memories
or Uniform Block Flash Memories(Normal Flash Memories)?
The sizes of the sectors are only important, when you are going to erase
them (or when you want to run a real filesystem on top of it, like JFFS2).
When you read this memory type (=run code from it), they are unimportant.
Hope it helps
Juergen
.
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