Intel
®
81341 and 81342—Address Translation Unit (PCI Express)
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
260
Order Number: 315037-002US
3.4.2
Outbound Byte Swapping
When enabled, the swapping occurs as described in
Swapping for Transaction with Byte Count of 1” on page 260
,
Byte Swapping for Transactions with Byte Count of 2” on page 260
“Outbound Byte Swapping Transaction with Byte Count of 3 or Larger” on page 260
.
The bytes are swapped within a 32-bit DWORD and the type of byte swapping
performed is determined by the transaction byte count. For Byte Count of 3 or larger
transactions, no byte swapping is performed.
Note:
The byte swapping capability of the ADMA unit should be used to swap bytes within
each DWORD for PCI-to-Memory Read/Write DMA transfers.
Figure 30. Outbound Byte Swapping for Transaction with Byte Count of 1
Figure 31. Outbound Byte Swapping for Transactions with Byte Count of 2
Figure 32. Outbound Byte Swapping Transaction with Byte Count of 3 or Larger
Byte 0 Byte 0
Word 0 [31:24] Word 0 [23:16]
Word 0 [15:8]
Word 0 [7:0]
Word 0 [7:0]
Word 0 [15:8]
Word 0 [23:16] Word 0 [31:24]
32-Bit Word on Internal Data Bus
32-Bit Word on PCI Bus
+3
+2
+1
+0
B6199-01
Byte 0 Byte 0
Word 0 [31:24] Word 0 [23:16]
Word 0 [15:8]
Word 0 [7:0]
Word 0 [15:8]
Word 0 [7:0]
Word 0 [31:24] Word 0 [23:16]
32-Bit Word on Internal Data Bus
32-Bit Word on PCI Bus
+3
+2
+1
+0
B6200-01
Byte 0 Byte 0
Word 0 [31:24] Word 0 [23:16]
Word 0 [15:8]
Word 0 [7:0]
Word 0 [31:24] Word 0 [23:16]
Word 0 [15:8]
Word 0 [7:0]
32-Bit Word on Internal Data Bus
32-Bit Word on PCI Bus
+3
+2
+1
+0
B6201-01