Mike Skinner

Problem with MC9S12A512 - HC12 - Memory at FF00-FFFF (Vector Table)

Discussion created by Mike Skinner on Sep 12, 2007
Latest reply on Sep 14, 2007 by Steve Mcaslan
Hi All,
 
I think there are some discrepancies in the Motorola technical documents for the MC9S12A512, and probably many other variants....
 
The overview picture of the Memory map shows that memory at location FF00 - FFFF is reserved for the Vector Table.
 
in the detailed memory map show preceeding this table it states that the memory C000 - FFFF contains 256 bytes at FF80 - FFFF (obviously this doesn't add up...).
 
This information is echoed in the vector table detailed in section 5 - Resets and interrupts (Table 5.2.1) which details all vectors from FF80 - FFFF.
 
My assumption is that the many different variants with differing peripherals etc use more or less vector entries. The space that isn't assigned to the vector table (i.e. in the A512 device, space from FF00 - FF7F) doesn't seem to be accessible as "ordinary" rom.
 
This does all seem obvious in retrospect, but it has been the very annoying and difficult to track source of a intermittent corruption problem in my project!
 
Could someone please confirm my suspicions (and my sanity) that:
1) The reserved vector table is from memory address FF00 - FFFF, not FF80 - FFFF (i.e. the actual used vectors)?
2) That unused vector space is unusable space.
 
Many thanks,
Mike.
 

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