Peripheral Bus
2-22
2.7.2
CPU Wait States
Isolated peripheral bus controller accesses from the CPU causes six CPU wait
states. These wait states are inserted to allow pipeline registers to break up
the paths between traversing the on-chip distances between the CPU and
peripherals as well as for arbitration time.
2.7.3
Arbitration Between the CPU and the DMA Controller
As shown in Figure 2–5 and Figure 2–6, the peripheral bus controller performs
arbitration between the CPU and the DMA controller for the peripheral bus.
Like internal data access, the PRI bits in the DMA controller determine the
priority between the CPU and the DMA controller. If a conflict occurs between
the CPU (via the data memory controller) the lower priority requester is held
off until the higher priority requester completes all accesses to the peripheral
bus controller. The peripheral bus is arbitrated as a single resource, so the low-
er priority resource is blocked from accessing all peripherals, not just the one
accessed by the higher priority requester.