Programming
4-10
Address Consistency
Address consistency, or address coherency, refers to communications between the
XVME 689-VR7 and the VMEbus in which both architectures' addresses are the same for
each byte. In other words, the XVME 689-VR7 and the VMEbus memory images appear
the same. Address consistency is desirable for byte-oriented data such as strings or video
image data. Consider the example of transferring the string
Text
to the VMEbus memory
using a 32-bit transfer in Figure 4-4.
Figure 4-4 Maintaining Address Consistency
Notice that the data byte at each address is identical. To achieve this, the data bytes need
to be swapped as they are passed from the PCI bus to the VMEbus. To maintain address
consistency, enable the byte-swapping buffers by setting bits 6 and 7 of the Flash Paging
and Byte Swap register (register 234h) to
0
(see p. 2-4).
Summary of Contents for XVME-689-VR7
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