Hi Ben,
first I think the BCD-byte is not the best way to manage the lookup
table, because it is difficult to get the base address of the block.
what i mean is:
to get the actual base address you take the base address of the first
block and the number of the key multiplied by 5 to the base.
if the number of the key is a BCD-byte multiplication is not that easy as
it would be with a binary byte.
another point:
to get the column number of the key you just need one cjne.
take the byte and compare it to 01h.
if it is not equal shift it right one time and compare it again to 01h
do that loop until your byte matches 01h and count the loops.
the result is multiplied by 8.
then add the row byte to that and you get the number in binary.
Christian