Booting MC68HC811 from external ROM/EEPROM

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Hello !


I've now read some of the datasheet and appnotes from the Motorola
website but I'm not sure if the MC68hc811 is the right thing for me.
(btw, i've already built some embedded systems but all with 80(c)31/51)

Now I know that my mcu can boot in "bootstrap mode" and in this mode i
can program the EEPROM. But what do I have to do to make it boot from
external ROM? Do I have to use the "expanded mode" and write only
BRA $ROM into the EEPROM ?


Maybe this sounds a bit stupid, but until now all I had to do was make a
board, burn an (E)EPROM, put it in and there we go.


Thank you anyway for you comments.


Simon.


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Re: Booting MC68HC811 from external ROM/EEPROM
Hi,
Which 68HC11 have you ? 68HC811E2 ?
In the 68HC11 family, the internal ressources (RAM, registers, EEPROM,..)
are "more important" than external ressources.
If you want boot on a external memory, you need external memory for the
vectors ($ffd6 $ffff). So, if it's a 68HC811E2, you have to move the
internal EEPROM (standard = $F800-$ffff).
In your code, you need :

org $fffe
fdb $8000 (if the start of your code is $8000)

org $8000
...
...
Regards,

Yvan

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