Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Reference Number: 306262-004US
723
HSS Coprocessor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
13.0
HSS Coprocessor
13.1
Overview
This document outlines the functional description of the HSS coprocessor.
The functionality supported by the High-Speed Serial (HSS) interfaces are tightly
coupled with the code written on the Network Processor Engine (NPE) core. This
chapter details the full hardware capabilities of the HSS interfaces contained within the
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors. The features
accessible by the user are described in the Intel
®
IXP400 Software Programmer’s
Guide and may be a subset of the features described below.
The HSS coprocessor enables the IXP45X/IXP46X network processors to communicate
in a Time Divisible Multiplexed (TDM) bit serial fashion with external chips. The HSS
interfaces are six-wire, serial interfaces that can operate at speeds from 512 KHz to
8.192 MHz.
The NPEs core controls each HSS interface. By programming certain parameters to the
HSS interfaces — such as frame length/offset, frame signal polarity, and data
endianness — the interfaces can be configured to support a variety of bit serial
protocols. The bit streams protocols that the hardware supports are T1, E1, GCI, MVIP.
The HSS hardware also has the ability to interface with certain xDSL framers. The HSS
is the interface between the NPE Core and an external device (usually classified as a
framer), which uses one of the above protocols.
For a list of supported protocols supported by the current software release, see the
Intel
®
IXP400 Software Programmer’s Guide.
Note:
In this document, the NPE (Network Processing Engine) microprocessor core is also
referred to as PSM or PSM2. The preferred term is NPE core.
Each HSS core contains 5 RX FIFOs, 4 RX FIFOs are for HDLC and are each two words
in length, these are further divided into two buffers, which are each 1 word in length.
These two buffers act in a ping-pong fashion.
The 4 FIFOs TX/RX can be configured to behave like two or one TX/RX FIFO, see
and Lookup Tables” on page 727
for more details. The TX FIFOs are identical in size and
numbers to the RX FIFOs.
The fifth RX FIFO is for VOICE and is four words in length, this is also split into two
buffers, which are each 2 words in length. These buffers also behave in a ping-pong
fashion, so the software processes two words (one buffer) at a time.
Each HSS core can be programmed by the NPE Core to perform the byte/frame
interleaving in the TX direction (MVIP), each core can also split up an incoming RX
MVIP stream into its constituent voice/HDLC streams (using the lookup tables
described below).
Two lookup tables 128*2 bits in size are present in each HSS core, 1 for the TX
direction and the other for the RX direction. These tables indicate if an incoming/
outgoing stream consists of HDLC/VOICE/56K or unassigned timeslots (bytes), the