Renesas rl78 User Manual

 

RL78/G1A 

CHAPTER  25   FLASH  MEMORY 

If rewriting the boot area failed by temporary power failure or other reasons, restarting a program by resetting or 

overwriting is disabled due to data destruction in the boot area. 

The boot swap function is used to avoid this problem. 

Before erasing boot cluster 0

, which is a boot area, by self-programming, write a new boot program to boot cluster 1 

in advance. When the program has been correctly written to boot cluster 1, swap this boot cluster 1 and boot cluster 0 by 

using the set information function of the firmware of the RL78 microcontroller, so that boot cluster 1 is used as a boot area.  

After that, erase or write the original area, boot cluster 0. 

As a result, even if a power failure occurs while the area is being rewritten, the program is executed correctly because it 

is booted from boot cluster 1 to be swapped when the program is reset and started next. 

 

Note  A boot cluster is a 4 KB area and boot clusters 0 and 1 are swapped by the boot swap function. 

 

 

Boot program

(boot cluster 0)

New boot program

(boot cluster 1)

User program

Self-programming 
to boot cluster 1

Self-programming 
to boot cluster 0

Execution of boot 
swap by firmware

User program

Boot program

(boot cluster 0)

User program

New user program

(boot cluster 0)

New boot program

(boot cluster 1)

User program

New boot program

(boot cluster 1)

Boot program

(boot cluster 0)

User program

X X X X X H

0 2 0 0 0 H

0 0 0 0 0 H

0 1 0 0 0 H

Boot

Boot

Boot

Boot

 

 

In an example of above figure, it is as follows. 

Boot cluster 0:  Boot area before boot swap 

Boot cluster 1:  Boot area after boot swap 

 

R01UH0305EJ0200  Rev.2.00 

 

 

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Jul 04, 2013