Programming the VMEbus Interface
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VMEbus Access to Universe Registers
As mentioned earlier, the Universe can be programmed to make its registers
accessible from the VMEbus. The Universe will power-up with VMEbus access to its
registers disabled, and it can be later programmed by application software to enable
them for VMEbus access. This functionality is controlled by programming the
VRAI_CTL and VRAI_BS registers.
PCIbus Access to Universe Registers
The Universe is defined as a PCI device, therefore it must provide a standard set of 64
DWORD-wide registers within the PCI Configuration Space. They are selected by
asserting the Universe IDSEL signal on a Configuration Space access. Since the
Universe registers consume a 4K block of memory, only the first 256 registers can be
accessed through Configuration Space. The remaining registers must be accessed
through memory or I/O space.
This 4KB block is also larger than the available area left in the I/O space. Therefore,
the registers are memory mapped. The base address of the registers must reside on a
64KB boundary, so they are placed at E0000h. The entire register set is accessible in
the E0000h-E3FFFh range.
For More Programming Information…
Complete programming information about the Tundra Universe chip is maintained in
the most current version of the Universe User Manual, available online at
http://www.newbridge.com/Tundra/Products/Bus/BPI/Univdn.html
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