PI7C7300DNAE Pericom Semiconductor, PI7C7300DNAE Datasheet - Page 47

• Manufacturer Part Number: PI7C7300DNAE
• Description: IC PCI-PCI BRIDGE 3PORT 272-BGA
• Manufacturer: Pericom Semiconductor

Specifications of PI7C7300DNAE

• Applications: *
• Interface: *
• Voltage - Supply: *
• Package / Case: 272-PBGA
• Mounting Type: Surface Mount
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 3 V to 3.6 V
• Supply Current (max): 660 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5.3.2
Pericom Semiconductor
PREFETCHABLE MEMORY BASE AND LIMIT ADDRESS
REGISTERS
Locations accessed in the prefetchable memory address range must have true memory-
like behavior and must not exhibit side effects when read. This means that extra reads to
a prefetchable memory location must have no side effects. PI7C7300D pre-fetches for all
types of memory read commands in this address space.
The prefetchable memory base address and prefetchable memory limit address registers
define an address range that PI7C7300D uses to determine when to for- ward memory
commands. PI7C7300D forwards a memory transaction from the primary to the
secondary interface if the transaction address falls within the prefetchable memory
address range. PI7C7300D ignores memory transactions initiated on the secondary
interface that fall into this address range. PI7C7300D does not respond to any
transactions that fall outside this address range on the primary interface and forwards
those transactions upstream from the secondary interface (provided that they do not fall
into the memory-mapped I/O range or are not forwarded by the VGA mechanism).
The prefetchable memory range supports 64-bit addressing and provides additional
registers to define the upper 32 bits of the memory address range, the prefetchable
memory base address upper 32 bits register, and the prefetchable memory limit address
upper 32 bits register. For address comparison, a single address cycle (32-bit address)
prefetchable memory transaction is treated like a 64-bit address transaction where the
upper 32 bits of the address are equal to 0. This upper 32-bit value of 0 is compared to
the prefetchable memory base address upper 32 bits register and the prefetchable
memory limit address upper 32 bits register. The prefetchable memory base address
upper 32 bits register must be 0 to pass any single address cycle transactions
downstream.
Prefetchable memory address range has a granularity and alignment of 1MB. Maximum
memory address range is 4GB when 32-bit addressing is being used. Prefetchable
memory address range is defined by a 16-bit prefetchable memory base address register
at configuration offset 24h and by a 16-bit prefetchable memory limit address register at
offset 26h. The top 12 bits of each of these registers correspond to bits [31:20] of the
memory address. The lowest 4 bits are hardwired to 1h. The lowest 20 bits of the
prefetchable memory base address are assumed to be 0 0000h, which results in a natural
alignment to a 1MB boundary. The lowest 20 bits of the prefetchable memory limit
address are assumed to be FFFFFh, which results in an alignment to the top of a 1MB
block.
Note: The initial state of the prefetchable memory base address register is 0000 0000h.
The initial state of the prefetchable memory limit address register is 000F FFFFh. Note
that the initial states of these registers define a prefetchable memory range at the bottom
1MB block of memory. Write these registers with their appropriate values before setting
either the memory enable bit or the master enable bit in the command register in
configuration space.
To turn off the prefetchable memory address range, write the prefetchable memory base
address register with a value greater than that of the prefetchable memory limit address
register. The entire base value must be greater than the entire limit value, meaning that
the upper 32 bits must be considered. Therefore, to disable the address range, the upper
Page 47 of 107
3-PORT PCI-TO-PCI BRIDGE
November 2005 - Revision 1.01
PI7C7300D