Hi,

Attached files fixes some problems with nvram emulation:
- whole nvram was erased in some conditions
- fix out of range accesses
- improve reading speed by keeping contents in memory

Changelog v1 to v2
- rename capacity to chip_size
- write nvram contents during initialization only the first time
Changelog v2 to v3
- write nvram contents at each initialization, because 'wb' mode
   cleans the file

Thanks Aurelien for your comments.

Hervé