Sharp 28JS-74E Service Manual page 71

3. How to rewrite data in NVM.
The NVM (Non Volatile Memory) is a read/write device which function is to keep data even in the case of TV set is
switched off.
Part of these data is recovered every time the TV is switched on, and, of course, if user makes any change in the
user settings (i.e brightness, contrast, etc..).
The NVM data could be corrupted if any external destructive action is carried out (Sparks of high voltage) or if a
problem happens to the IC itself (defective IC or damaged IC). In order to keep the data uncorrupted, several
protection countermeasures are implemented; one of them is to have a copy of all the NVM relevant parameters in
the FLASH (which keeps the software for the microcontroller). So, the procedure to follow if the NVM IC is damaged
or the data is lost is the following:
a) If the NVM IC is substituted for a new (BLANK) one, it is possible to write the NVM asking for the file which
corresponds to the model or let the microcontroller write the default data which is written inside. This
process is automatically carried out when the blank device (NVM) is soldered and TV is switched on for
first time after the modification. The TV starting time is longer than normally due to the rewriting procedure.
In both cases a new geometry adjustment should be done because of CRT and chassis tolerances.
b) If the NVM is corrupted and some data is lost, there are internal software protection to recover the data
related with configuration of ICs but user data can be lost (some channel data or user settings for video,
audio etc..). It is possible to recover this data forcing an auto installation and setting the user settings
again.
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