A circuit arrangement for bus arbitration alters the sequence in which
device requests are arbitrated with respect to each other and to a
previous arbitration sequence. To this end, an arbiter grants access to a
first group of devices according to a predetermined sequence. The arbiter
then automatically alters the sequence for a second group of devices,
granting access to the bus for the second group according to the altered
sequence. These features allow the order in which the arbiter sequences
through the groups to be automatically varied with respect to each other,
diminishing the likelihood of lockout.