Ok, I've spotted what you're doing wrong. Somehow, you seem to have
misunderstood the concept of big-endianness. The _most_ significant
part of the address goes into the _lowest_ memory location ($7D), the
_least_ significant part of the address goes into the _highest_
memory location ($7F). So


Alessandro> ld lev_offs_lo
Alessandro> st $7d ; $7d = lo-offset current
write-address
Alessandro> ld lev_offs_hi
Alessandro> st $7e ; $7e = hi-offset current
write-address
Alessandro> mov #0,$7f ; $7f = 0 (24 bit big endian)

should be

ld lev_offs_lo
st $7f ; $7f = lo-offset current write-address
ld lev_offs_hi
st $7e ; $7e = hi-offset current write-address
mov #0,$7d ; $7d = 0 (24 bit big endian)


// Marcus