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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
585
Memory Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
11.2.1.1.2
Internal Bus Ports (North and South AHB)
The two Internal Bus Ports (North AHB and South AHB) provide the connection to the
DDRI SDRAM from the Internal AHB Buses. All peripheral unit transactions targeting
the DDRI SDRAM are claimed by these ports. Also all accesses to MMR space will be
through the south AHB Internal bus port, this includes Intel XScale processor MMR
accesses.
11.2.1.2
Address Decode Blocks
Address Decode is performed for transactions from input ports to determine if the MCU
should claim the transaction. There are two address ranges the MCU ports can claim
transactions: DDRI SDRAM memory space and Memory-Mapped Register (MMR) space.
11.2.1.2.1
DDRI SDRAM Memory Space
The DDRI SDRAM memory space is defined as 0x0000_0000 to 0x3FFF_FFFF (1GB) for
the IXP45X/IXP46X network processors.
Note:
At boot time, the expansion bus resides at location 0000_0000h instead of the DDRI
SDRAM. The DDRI controller must be configured first and the expansion bus decode
programmed to sit at its higher address before DDRI transactions can be initiated. See
Section 12.4.1.1, “Expansion Bus Address Space”
for details.
11.2.1.2.2
Memory-Mapped Register Space
The MCU MMR memory space is CCFF E500H to CCFF E5FFH and CCFF F500H to CCFF
F5FFH. See
Section 11.6, “Register Definitions”
for details.
The Address Decode for each port is based on the same registers which are only
accessible from the South AHB internal bus.
Read and write accesses to all Configuration/Status registers (CSR) must be single
word transfers. Byte, half-word, burst, or coalesced transfers are not supported and
result in unpredictable operation. All CSR reserved bits must be written with zero.
Each port decodes inbound transactions for these address ranges. The Address Decode
blocks determine how the Memory Controller responds to inbound transactions. The
details of the address decode for each port is described below.
11.2.1.2.3
Core Processor Port Address Decode
The address decode block for the Core Processor transactions resides in the BIU. The
Core MCU port therefore does not require any decode, and will process any transaction
received from the BIU via the Core MCU Port.
If the Core Processor Memory Transaction Queue is disabled (refer to
bit 31 MPI_EN) all core transactions are directed to the Core
Internal Bus Transaction Queue of the BIU, and would not be sent to the Core MCU port
(refer to
). Therefore core transactions which address the DDRI
SDRAM, will be claimed by the IB port of the MCU and processed via that port as any
other IB transaction. It is recommended that MCU transaction queues are not disabled.
11.2.1.2.4
Internal Bus Port Address Decode
Internal Bus transactions are decoded to determine if they address the DDRI SDRAM
Memory Space or MCU MMR Space. If the transaction addresses either of these two
spaces, the transaction is claimed by one of the Internal Bus Ports. (Only South AHB
port can claim MMR accesses.) If the transaction addresses the DDRI SDRAM Memory