Например, для шины swire используется lib.swb.
Процедура wr_reg (a, d, size):
sub wr_reg (a, d, size)
sss_ah = a >> 8
sss_al = and (a, 0xff)
sss_d3 = d >> 24
sss_d2 = and (d >> 16, 0xff)
sss_d1 = and (d >> 8, 0xff)
sss_d0 = and (d, 0xff)
//print sss_ah, sss_al, d...