Revision 1.02 – June 27, 2006
S5935 – PCI Product
Data Book
64-Bit Endian Conversion
Because the S5935 interfaces to a 32-bit PCI bus, special operation is required to handle 64-bit data endian con-
version. Figure 2c shows 64-bit endian conversion. The S5935 must know whether the lower 32-bits enter the
FIFO first or the upper 32-bits enter the FIFO first. INTCSR D31:30 identify which method is used by the applica-
tion. These bits toggle after each 32-bit operation to indicate if half or all of a 64-bit data operation has been
completed. The initial state of these bits establishes the loading and emptying order for 64-bit data during
operation.
Figure 2c. 64-bit Endian Conversion
DESTINATION
D 31-24
SLR
D 23-16 D 15-8
D 7-0
SLR
READ ORDER:
BYTES 3-0 FIRST
OR
BYTES 7-4 FIRST
SEE TEXT
SLR
SLR
BYTE 7
BYTE 6
BYTE 3
BYTE 2
BYTE 5
BYTE 1 BYTE 0
BYTE 4
BYTE 6
BYTE 2
BYTE 7
BYTE 5
BYTE 3
BYTE 1
BYTE 4
BYTE 0
LOAD ORDER:
BYTES 3-0 FIRST
OR,
BYTES 7-4 FIRST
SEE TEXT
D 31-24
SOURCE
D 15-8
D 7-0
D 23-16
136
DS1527
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