Outbound Transfers; August; Expansion Bus Controller - Intel IXP45X Developer's Manual

12.3 Block Diagram
Figure 123. Expansion Bus Controller
Configuration Bits
AHB Slave
AHB Interface
AHB Master
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).
® ®
Intel IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
650
®
Intel IXP45X and Intel
Expansion Master
Expansion Slave

Expansion Bus Controller

Expansion Arbiter
®
IXP46X Product Line of Network Processors—Expansion Bus
CS1
CS0
Intel Motorola
Synchronous Multiplexed
StrataFlash SRAM
Expansion Bus
External External
Master Master
0 1
Arbitration Bus
Controller
CS7
Micron ZBT
External
Master
3
B4230-01

August 2006

Order Number: 306262-004US