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Topic: Atmega2560 r2 What is boot start address (Read 740 times) previous topic - next topic

chrischa

Hello,
I try to make a bootloader for my Atmega2560 r2
Fuses are low FF, high D8, Ext FF
Lock bits are 0F

option for link is : -Wl,--section-start=.text=0x1F000

Is 1F000 good for a 8kb bootloader?

Thank you.

CrossRoads

See the datasheet.
Table 30-4 shows High Byte fuse bits 2,1 select the boot size.
With the bits at 0 0, Table 29-7 says 4096 works (8192 bytes),  occupying:

0x7000 - 0x7FFF
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

chrischa

Ok I saw datasheet.

I tried with 0x7000, without success.

I also tried 0xE000 witch is 7000 * 2, without success...

I don't understand why 7000? Atmega 2560 has 256Kb of flash. 256*1024 = 262144, if 8Kb is removed at the end, it's 262144-(8*1024) = 253952, it's 0x3E000, divided by 2 (word access) it's 0x1F000.

I tried also 1F000, it's always the same result, program boots always at 0.

Then I tried 3E000 and it works fine.

Thank you for all




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