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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Functional Overview
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
60
Reference Number: 306262-004US
within the EAU) which the EAU state machine accesses and also uses for temporary
registers. The arithmetic operations supported by the EAU are used by software
executing in the host processor to build larger cryptographic functions such as signing
and verification procedures. Since the EAU executes only one operation at a time, the
host processor must serialize the required operations to the EAU.
The EAU begins operating after the host processor has moved data into the EAU RAM
and loads the EAU’s command register with an appropriate command. After executing
the command, the EAU appropriately sets its status bits and waits idle until it receives
another command from the host processor.
The RNG unit provides a digital random number generation capability. It uses a LFSR
(Linear Feedback Shift Register) to generate a sequence of pseudo-random bits. These
sequences are shifted into a FIFO of 32-bit words, which may be read sequentially from
the random number register. A new word is generate every 32 clocks, and the RNG will
buffer 16 of these words at a time. The output of the RNG should be passed through
the SHA engine for added randomness. The host processor (Intel XScale processor) is
responsible for implementing this SHA based random number generation. The LFSR
also allows one entropy source. The entropy source is fed in from a PN sequence
generator which has a period of 2^42 - 1. The coefficients for the PN sequence is
chosen such that it produces the maximal sequence length. The coefficients are not
mentioned for security reasons. The coefficients for the 128 stage LSFR are similarly
not mentioned here for security reasons.
The SHA unit is used to provide added randomness to the random numbers produced
by the random number generator (RNG). It is the responsibility of the Intel XScale
processor to get the data from the RNG, provide it to the SHA unit, and retrieve the
data after it is complete.
2.1.20
Queue Manager
The Queue Manager provides a means for maintaining coherency for data handling
between various processor cores contained on the IXP45X/IXP46X network processors
(NPE to NPE, NPE to Intel XScale processor, etc.). It maintains the queues as circular
buffers in an embedded 8-Kbyte SRAM. The Queue Manager also implements the status
flags and pointers required for each queue.
The Queue Manager manages 64 independent queues. Each queue is configurable for
buffer and entry size. Additionally status flags are maintained for each queue.
The Queue Manager interfaces include an Advanced High-performance Bus (AHB)
interface to the NPEs and Intel XScale processor (or any other AHB bus master), a Flag
Bus interface, an event bus (to the NPE condition select logic), and two interrupts to
the Intel XScale processor.
The AHB interface is used for configuration of the Queue Manager and provides access
to queues, queue status, and SRAM. Individual queue status for queues 0-31 is
communicated to the NPEs via the flag bus. Combined queue status for queues 32-63
are communicated to the NPEs via the event bus. The two interrupts, one for queues 0-
31 and one for queues 32-63, provide status interrupts to the Intel XScale processor.
2.2
Intel XScale
®
Processor
The Intel XScale technology is compliant with the Intel
®
StrongARM
*
Version 5TE
instruction-set architecture (ISA). The Intel XScale processor — shown in
designed with Intel, 0.18-µ production semiconductor process technology. This process
technology — with the compactness of the Intel
®
StrongARM
*
RISC ISA — enables the
Intel XScale processor to operate over a wide speed and power range, producing
industry-leading mW/MIPS performance.