Byte Swapping Capability
rev 2.0
SFPCI-VME SERIES User’s Guide and Installation Manual
47
6.3.1 Byte Swapping for bytes:
FIGURE 18
Byte Swapping For Bytes
At this time the swapping for byte access remains unchanged. This means single bytes
access on the PCI side and VME side are the same as in no swapping. This can be seen
from the table 15. Though the charateristics of VME bus “swap” the bytes automatically
to upper byte instead of writing to lower byte and vice versa. This can be seen from the
following print out. First byte (0x12) written will appear after Universe as upper byte at
0x00000000, and second byte (0x34) is written to lower byte at address 0x00000001,
and so forth.
Linux VMIC vme_poke:
vme_poke -a VME_A32SD -A 0x00 -d VME_D8 -F data_b
data_b: 0x12 0x34 0x56 0x78
Byte write VME analyzer prinout:
TRIG 0.00 us - 00000000 ....12.. W UBYTE OK OK ------- 1 1 0D 1
1 0.52 us - 00000001 ......34 W LBYTE OK OK ------- 1 1 0D 1
2 0.48 us - 00000002 ....56.. W UBYTE OK OK ------- 1 1 0D 1
3 0.52 us - 00000003 ......78 W LBYTE OK OK ------- 1 1 0D 1
Universe II
D[7:0]
D[15:8]
D[23:16]
D[31:24]
D[7:0] / D[23:16]
D[15:8] / D[31:24]
Xilinx
XC95xx
Byte Swap
Logic
DS1* DS0* A1 LW*
VD[31:24]
VD[23:16]
VD[15:8]
VD[7:0]
VME
Devices
DS1* DS0* A1 LW*
PCI Bus
