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Using a Flash ROM with the 21554 Non-Transparent PCI-to-PCI Bridge Application Note
The 21554 supports the attachment of standard parallel 8-bit Flash ROM.
The PCI expansion ROM base address register (BAR), at offset 30h, is
offered with ROM sizes ranging between 4 KB and 16 MB. If required, this
feature can provide the PCI expansion ROM interface for the subsystem. If
the subsystem does not need this capability, the PCI expansion ROM
BAR can be disabled by clearing bit 0 of this register.After configuration of the 21554's primary PCI interface, the parallel ROM can be accessed by the host in the memory address range assigned by the PCI expansion ROM BAR. The Flash ROM is not directly accessible from the memory address space of the secondary PCI interface. However, it can be accessed indirectly from both the primary and secondary PCI interface using the 21554's command and status registers (CSRs).
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