AN2077 データシートの表示（PDF） - STMicroelectronics

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AN2077

EEPROM Emulation with STR71x

STMicroelectronics 

EEPROM Emulation with STR71x

3.1.2 Minimum software to be copied into the on-chip RAM

The minimum software to be copied into the on-chip RAM is:

– Functions issuing the erasing and or programming commands to the STR71x embedded-

Flash controller,

– Functions polling the Flash status register for detecting the completion of the command and

for error detection (see detailed specification),

– Watchdog refresh (if activated).

3.2 DATA PROGRAMMING / ERASING WITH STR71XF

Flash programming/erasing in the field, requires the ability to deal safely with all the possible

events that may occur in the application.

This analysis is application-dependent and has to be carefully conducted by the user. This

section assumes that users have experience with all the generic aspects of field reprogram-

ming; this section will focus only on STR71xF specific events.

3.2.1 Flash field reprogramming

This subsection gives useful information for the field reprogramming of data. This advice is not

specific to STR71x but is generic to any embedded application that reprograms itself a Data-

set.

The main points to control during Flash programming/erasing are:

– completion of the self-programming/erasing process,

– events that may interrupt the reprogramming process.

3.2.1.1 Completion of the programming process

The programming process is completed when the last word to be programmed has been pro-

grammed correctly (i.e.: the status returned by the Flash is OK). Usually, the last word pro-

grammed is an update of the status word (or status bits) of the new Data-set.

If, for any reason, the programming process is interrupted, at the next restart, the value read

may be either erroneous or good but with a limited retention time.

This should influence how users code the status bits and how supply failures are detected

(early warning) or prevented (CPU controlled voltage regulator). It is difficult to be specific

here as choices will depend on application requirements and constraints.

3.2.1.2 Completion of the erasing process

As explained in Section 1.3, the completion of the erasing process before programming in a

bank is very important. Single bit information to record a successful erase process should be

avoided. Whenever possible:

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