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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Expansion Bus
Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
650
Order Number: 306262-004US
12.3
Block Diagram
12.4
Theory of Operation
The Expansion bus controller on the IXP45X/IXP46X network processors supports both
of the following:
• outbound transfers that are initiated by an AHB master that targets Expansion bus
targets
• inbound transfers that are initiated by an external Expansion bus master that
targets internal IXP45X/IXP46X network processors slaves or external Expansion
bus targets.
The Expansion bus controller arbiter has request/grant lines to support four external
masters. An option to support an external arbiter is also supported. The Expansion data
bus is 32 bits wide and the address bus is 25 bits wide.
Since the Expansion bus controller has only 1 outbound transaction queue, outbound
accesses all complete in order. Similarly, all inbound transactions complete in order. The
Expansion bus controller does not do any order checking between inbound and
outbound transfer and relies on software for correct ordering.
12.4.1
Outbound Transfers
For outbound data transfers, the Expansion bus controller occupies 256 Mbytes of
address space in the memory map of the IXP45X/IXP46X network processors and
contains a 1-deep address queue, an 8-word write data fifo, and an 8-word read data
FIFO. Eight chip selects are supported to allow up to eight independent external devices
to be connected. The address space for each chip select is up to 32 Mbytes (16 MBytes
Intel
®
IXP400 Software-compatibility mode).
Figure 123. Expansion Bus Controller
Expansion Bus Controller
B4230-01
Intel
Synchronous
StrataFlash
Motorola
Multiplexed
SRAM
Micron ZBT
External
Master
1
External
Master
0
Arbitration Bus
Expansion Master
Expansion Slave
AHB Slave
AHB Master
AHB Interface
Expansion Arbiter
Expansion Bus
Configuration Bits
External
Master
3
CS0
CS7
CS1