Bus access control for a multi-host system using successively

Abstract

Any host requesting acccess to the bus must, on its first attempt, wait for N arbitration delay periods after the bus becomes available before attempting to take control of the bus. If another host takes the bus before completion of the arbitration delay period, the host must wait till the next time the bus becomes available. The arbitration delay count is decreased by one for each successive attempt, until the host either gains control of the bus or the aribration delay period goes to zero. At this point it may attempt to take control of the bus as soon as the bus becomes available. If another higher priority host reaches an arbitration delay count of zero during the same arbitration delay count period, the host will be denied and will wait for the next time the bus becomes available, again with an arbitration delay count of zero. The host in question will eventually gain control of the bus as each higher priority host which has denied it access to the bus must begin its next attempt at gaining the bus with a delay count of N. The host in question will thereby eventually be the highest priority host which has reached an arbitration delay count of zero.