Xycom XVME-678 Manual page 100

Chapter
4 -
Programming
4.8.3 Numeric Consistency
Numeric consistency refers to the situation where the byte-ordering schemes described above must be
followed to maintain the value of a 16-bit or 32-bit quantity. Numeric consistency is desired for
transferring integer data, floating point data, pointers, etc. Consider the long word value 12345678H
stored at address "M" by both the XVME-678/688 and the VMEbus:
Address
78 M
12
56
M+1
34
34
M+2
56
12
M+3
78
XVM E -678/688
VMEbus
Figure 4-13. Maintaining Numeric Consistency
Notice that the internal data storage scheme for the Intel machine is different from that of the VMEbus
(i.e., the byte "78" is stored at location M in the Intel machine, while "78" is stored at location M
+
3 on
the VMEbus due to the inherent specification of each bus). However, the data bus connections are the
same between architectures and therefore the data must be passed straight through.
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