When the assembler is in unsegmented mode (specified with the
unsegm directive), an address takes up one word (16 bit)
sized register. When the assembler is in segmented mode (specified with
segm directive), a 24-bit address takes up a long (32 bit)
register. See Assembler Directives for the Z8000,
for a list of other Z8000 specific assembler directives.