Byte Swapping Capability
rev 2.0
SFPCI-VME SERIES User’s Guide and Installation Manual
49
6.3.3 Byte swapping for long words
FIGURE 20
Byte Swapping for long words
Byte swapping for long word requires swapping four bytes simultaneously. As shown in
the figure above, there is a one-to-one swapping for the four byte lanes. Along with
data, control signals such as DS1*, DS0*, A1, LW* are regenerated by Xilinx XC95xx
to appropriate values before VME devices/memory.
6.4 Byte Swapping For Interrupt Vector
Depending on different interpretations with different software application, interrupt
vector can be masked out, and byte swapping for interrupt vector could be treated
differently. Currently, SF_VME rev F. board treats the interrupt vector as in no
swapping scenario, regardless whether the board was set to swapping mode or non-
swapping mode. That means when interrupt vector comes in from the VME side, there
will be no byte swapping for the interrupt vector. In the case when the vector is a one
byte data, the Tundra Universe VME-PCI bridge on board will receive it as a lower byte
data.
Universe II
D[7:0]
D[15:8]
D[23:16]
D[31:24]
D[23:16]
D[31:24]
Xilinx
XC95xx
Byte Swap
Logic
DS1* DS0* A1 LW*
VD[31:24]
VD[23:16]
VD[15:8]
VD[7:0]
Devices
DS1* DS0* A1 LW*
PCI Bus
D[15:8]
D[7:0]
