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IDT PCI Bus Interface
PCI Configuration Registers
79RC32438 User Reference Manual
10 - 58
November 4, 2002
Notes
SIZE
Description:
Address Space Size.
This field indicates the size of the address space for the corresponding
PCI base address register. All bits greater than or equal to SIZE in PBAx may be modified. Bits
less than SIZE and greater than or equal to bit four always return a value of zero when read and
cannot be modified. Setting the SIZE field to a value less than eight results in all bits in the corre-
sponding PBAx register to take on the value zero. This effectively disables the PCI base address
register.
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
SB
Description:
Swap Bytes.
This bit controls byte swapping for PCI transactions that map to the local bus
through the PBAx register.
0x0 - No byte swapping
0x1 - Swap bytes
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
PP
Description:
Perform Prefetching.
This bit controls the prefetching behavior for PCI read transactions that
map to the local bus through PBAx.
0x0 - Do not perform prefetching for any transactions
0x1 - Perform prefetching as indicated by the MR, MRL, and MRM fields in this register
Initial Value:
0x1
Read Value:
Previous value written
Write Effect:
Modify value
MR
Description:
Memory Read Behavior.
This bit controls the behavior of PCI memory read transactions.
0x0 - Read data indicated by transaction (no prefetching)
0x1 - Treat memory read transactions as memory read line transaction
0x2 - Treat memory read transactions as memory read multiple transaction
0x3 - reserved
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
MRL
Description:
Memory Read Line Prefetching Behavior.
This bit controls the behavior of PCI memory read
line transactions.
0x0 - Prefetch data to end of cache line
0x1 - Treat memory read line transactions as memory read multiple transactions
Initial Value:
0x0