AMBA AHB

3.16 Implementing a wide slave on a narrow bus

The example in Figure 3-22 shows a wide slave being implemented on a narrow bus. Again only external logic is required and hence predesigned or imported blocks can be easily modified to work with a different width of data bus.

Figure 3-22 Wide slave on a narrow bus

3.16.1Masters

Bus masters can easily be modified to work on a wider bus than originally intended, in the same way that the slave is modified to work on a wider bus, by:

•multiplexing the input bus

•replication of the output bus.

However, bus masters cannot be made to work on a narrower bus than originally intended, unless there is some mechanism included within the master to limit the width of transfers that the bus master attempts. The master must never attempt a transfer where the width (as indicate by HSIZE) is wider than the data bus to which it is connected.