ICS1893BF Data Sheet Rev. E - Release
Chapter 6 Functional Blocks
6.2 Functional Block: Auto-Negotiation
The auto-negotiation logic of the ICS1893BF has the following main functions:
• To determine the capabilities of the remote link partner, (that is, the device at the other end of the link
segment’s medium or cable)
• To advertise the capabilities of the ICS1893BF to the remote link partner
• To establish a protocol with the remote link partner using the highest-performance operating mode that
they have in common
The design of the ICS1893BF Auto-Negotiation sublayer supports both legacy 10Base-T connections as
well as new connections that have multiple technology options for the link. For example, when the
ICS1893BF has the auto-negotiation process enabled and it is operating with a 10Base-T remote link
partner, the ICS1893BF monitors the link and automatically selects the 10Base-T operating mode – even
though the remote link partner does not support auto-negotiation. This process, called parallel detection, is
automatic and transparent to the remote link partner and allows the ICS1893BF to function seamlessly with
existing legacy network structures without any management intervention.
(For an overview of the auto-negotiation process, see Section 4.4, “Auto-Negotiation Operations”.)
6.2.1 Auto-Negotiation General Process
The Auto-Negotiation sublayer uses a physical signaling technique that is transparent at the packet level
and all higher protocol levels. This technique builds on the link pulse mechanism employed in 10Base-T
operations and is fully compliant with clause 28 of the ISO/IEC 8802-3 standard.
During the auto-negotiation process, both the ICS1893BF and its remote link partner use Fast Link Pulses
(FLPs) to simultaneously ‘advertise’ (that is, exchange) information on their respective technology
capabilities as follows:
1. For the auto-negotiation process to take place, both the ICS1893BF and its remote link partner must
first both support and be enabled for Auto-Negotiation.
2. The ICS1893BF obtains the data for its FLP bursts from the Auto-Negotiation Advertisement Register
(Register 4).
3. Both the ICS1893BF and the remote link partner substitute Fast Link Pulse (FLP) bursts in place of the
Normal Link Pulses (NLPs). In each FLP burst, the ICS1893BF transmits information on its technology
capability through its Link Control Word, which includes link configuration and status data.
4. Similarly, the ICS1893BF places the Auto-Negotiation data received from its remote link partner's FLP
bursts into the Auto-Negotiation Link Partner Ability Register (Register 5).
5. After the ICS1893BF and its remote link partner exchange technology capability information, the
ICS1893BF Auto-Negotiation sublayer contrasts the data in Registers 4 and 5 and automatically
selects for the operating mode the highest-priority technology that both Register 4 and 5 have in
common. (That is, both the ICS1893BF and its remote link partner use a predetermined priority list for
selecting the operating mode, thereby ensuring that both sides of the link make the same selection.) As
follows from Annex 28B of the ISO/IEC 8802-3 standard, the pre-determined technology priorities are
listed from 1 (highest priority) to 5 (lowest priority):
(1) 100Base-TX full duplex
(2) 100Base-T4. (The ICS1893BF does not support this technology.)
(3) 100Base-TX (half duplex)
(4) 10Base-T full duplex
(5) 10Base-T (half duplex)
ICS1893BF, Rev. E, 8/11/09
August, 2009
Copyright © 2009, IDT, Inc.
All rights reserved.
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