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Basic Bus: One initiator.

The most basic bus has one initiator and several targets. The initiator does not need to arbitrate for the bus since it has no competitors.

Bus operations are just reads or writes of single 32-bit words. In reality, most on-chip busses support burst transactions, whereby multiple consecutive reads or writes can be performed as a single transaction with subsequent addresses being implied as offsets from the first address.

Interrupt signals are not shown in these figures. In a SoC they do not need to be part of the physical bus as such: they can just be dedicated wires running from device to device.

Un-buffered wiring can potentially serve for the write and address busses, whereas multiplexors are needed for read data. Buffering is needed in all directions for busses that go a long way over the chip.

15: (C) 2008-11, DJ Greaves, University of Cambridge, Computer Laboratory.