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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Reference Number: 306262-004US
55
Functional Overview—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Some of the peripheral device types are SRAM, flash, ATM control interfaces, and DSPs
used for voice applications. (Some voice configurations can be supported by the HSS
interfaces and the Intel XScale processor, implementing voice-compression
algorithms.)
The expansion interface functions in two modes of operation:
• Legacy (16-bit, data mode)
• Enhanced (32-bit, data mode)
In the legacy mode of operation, the expansion interface is a 16-bit interface that
allows an address range of 512 bytes to 16 Mbytes, using 24 address lines for each of
the eight independent chip selects.
Accesses to the expansion bus interface consists of five phases. Each of the five phases
can be lengthened or shortened by setting various configuration registers on a per-
chip-select basis. This feature allows the IXP45X/IXP46X network processors to
connect to a wide variety of peripheral devices with varying speeds.
The expansion interface supports Intel or Motorola* microprocessor-style bus cycles.
The bus cycles can be configured to be multiplexed address/data cycles or separate
address/data cycles for each of the eight chip-selects.
Additionally, Chip Selects 4 through 7 can be configured to support Texas Instruments*
HPI-8 or HPI-16 style accesses for DSPs.
The expansion interface is an asynchronous interface to externally connected chips.
However, a clock must be supplied to the IXP45X/IXP46X network processors’
expansion interface for the interface to operate. This clock can be driven from GPIO 15
or an external source. The maximum clock rate that the expansion interface can accept
is 80 MHz.
By providing this legacy mode of operation, code developed for previous generations of
this platform becomes easily portable.
In the enhanced mode of operation, the expansion interface is a 32-bit interface that
allows an address range of 512 bytes to 32 Mbytes per chip select on the IXP45X/
IXP46X network processors, using 25 address lines for each of the eight independent
chip selects.
Additionally, in enhanced mode, the interface supports shared access to the internal
bus with external masters. This shared access is achieved with four request/grant pins
and an integrated arbiter. Not only can external devices access each other, but they can
also access the IXP45X/IXP46X network processors’ internal registers (including the
DDRI SDRAM interface).
The advantage to this feature is that shared memory access can be achieved by using
the DDRI SDRAM interface attached to the IXP45X/IXP46X network processors. This
lowers the system’s overall bill of materials.
Enhanced mode also supports synchronous transfers at speeds of up to 80 MHz with a
40-pF load. In addition to fully synchronous support, the enhanced mode also supports
burst transfers of up to eight-word lengths. The synchronous bus support is compatible
to Zero Bus Turnaround (ZBT) SRAM cycles for inbound/outbound transactions for both
read/write transactions.
Additionally, the outbound read transactions can support the Intel StrataFlash
®
Embedded Memory P30 synchronous-burst support.
Byte-wide parity is an optional configuration of this interface in enhanced mode of
operation.