SBus Basic Cycles

The following are definitions of the SBus basic transaction cycle for each bus.

Arbitration Phase--During this phase, masters request bus access. When there is contention between masters, the controller determines which master performs the next transfer. After arbitration, the controller is responsible for monitoring the transfer.

Translation Phase--The master and controller participate in conversion of the virtual addresses to physical address and selection signals that are used by the master and the slaves.

Extended Transfer Information Phase--This phase is used only for the cycles requested by the master that have a SIZ[2:0] value of Extended Transfer.

Transfer Phase--During the Transfer Phase (slave cycle), data is moved to or from the slave.

Dynamic Bus-sizing--This feature enables a master to communicate more easily with slaves of varying widths.

Burst Transfers--SBus burst transfer protocol is the same as that for SBus basic transactions, except that multiple words are transferred. Neither dynamic bus-sizing or varying-width slaves are allowed.

Extended Transfer Mode--These 64-bit transfers enable increased performance. Up to twice the bandwidth is possible, as the data path is twice as wide.