Arbitration (cont’d)

• Avoids starvation by doing arbitration in rounds

  • RQST/ must be high before device can request bus
  • all simultaneous requestors are taken care ofbefore others can request
  • bus is quiet after ACK/ and before next START/

• Fairness

  • all requestors in round are taken care of
  • master may monopolize the bus if it doesn't raise its RQST/ and
  • releases ARB/ lines – sometimes necessaryfor time critical actions

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