
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
Datasheet
151
Document Number: 249241
Revision Number: 010
Revision Date: 30-May-2006
4.11
DTE Discovery Process
The DTE discovery process is port dependent and must be enabled through software. The process
is implemented as a next page option to the auto-negotiation flow. When the process is enabled,
manual control of auto-negotiation next pages is not allowed. This feature applies to the
LXT9785E transceiver only.
The process depends upon an IP phone, or any other DTE capable of being powered remotely,
having a specific filter that passes NLPs and FLPs. This filter should be non-polarized to insure
that the latest status of Auto-MDIX operation does not effect operation. This filter attenuates
100 Mbps MLT3 signals and 10 Mbps Manchester-encoded signals, and must be bypassed when
power is applied to the IP phone.
Figure 29 shows a typical IP telephone system connection.
4.11.1
Definitions
The following terms are used throughout the DTE discovery sections:
Figure 29. Typical IP Telephone System Connection
Power
Outlet
Computer
12 3
45 6
78 9
*
8#
IP Telephone
UPS/
Generator
Power cable
SD
Po we r
Fa ult
1 234 56
7 8
9 1011 12
Link
Mo de
Link
13 14 15 16 17 18
19
21
20
2 2 23 2 4
Mo de Sel ec t
Fdx
Ac t
1X
2X
3X
4X
5X
6X
7X
8X
9X
10X
11X
12 X
1 3X1 4X
15 X1 6X
1 7 X1 8X
1 9X2 0X
21 X2 2X
2 3 X2 4X
10/100Bas e -T Po rts
100
Res et
C lear
Mod ul e Sta tus
Se l fTe st
Console
Pro Curve Swi tc h 24 24 M
HP J4122B
VoIP-Enabled Switch
Power
Outlet
Data only over
Category 5 cable
Power cable
Power and data over
Category 5 cable
Negotiation Process:
This includes auto-negotiation and parallel detection processes
System:
The switch system using the LXT9785E for DTE Discovery
Link Partner:
A device connected to the LXT9785E through twisted pair cables
DTE:
Data Terminal Equipment; any end-of-link partner
Standard Link Partner:
A link partner that is not requiring power over a Category 5 cable;
typically a PC
Remote-Power DTE:
Data Terminal Equipment requiring power over a Category 5 cable;
typically an IP telephone
Discovery:
The process of identifying the type of link partner present