3.17.1. Programmer's model

The funnel has a simple interface design to work with AHB devices. Only a small subset of the AHB signals is implemented on the interface, because the other signals can be connected directly between AHB masters and slaves.

The funnel has two interfaces:

Figure 3.42 shows an example application of the funnel.

Figure 3.42. Typical funnel connection

The funnel can only function correctly if the 64-bit AHB master does not issue transfers of 64-bit to the 32-bit slave. For 32-bit accesses or accesses at smaller width, the correct word of the data bus is routed to the 32-bit slave. You must use the downsizer module if the transfers cannot be guaranteed to be 32-bit or less. See 64-bit to 32-bit downsizer.

Funnel selected and accessing even word address

In the address phase of a transfer, the funnel stores bit [2] of the address bus, HADDR. During data phase, the stored HADDR2S, Haddrs2Delayed, determines the side of the HWDATA that must be routed to the 32-bit bus. HWDATA[31:0] is selected for even word addresses and HWDATA[63:32] for even word addresses.

For read transfers, the HRDATAM signal is routed to both HRDATAS[31:0] and HRDATA[63:32] and read by the 64-bit bus master.

Endianness

The funnel supports little-endian and word-invariant big-endian systems. It can be used in full big-endian mode by reversing the polarity of the HWDATA multiplexor.

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