VSC8601 Datasheet
Functional Descriptions
The VSC8601 device is compatible with switch designs that are intended for use in
systems that supply power to Data Terminal Equipment (DTE) using the MDI or twisted
pair cable, as described in clause 33 of the IEEE standard 802.3af. The following
illustration shows an example of this type of application.
Figure 6.
Inline Powered Ethernet Switch Diagram
Processor
Gigabit Switch
RGMII
Interface
Control
SMI
PHY_0
PHY_1
PHY_n
Inline
Power
Supply Unit
X-former
X-former
X-former
RJ-45
I/F
RJ-45
I/F
RJ-45
I/F
Cat5
The following procedure describes the process that an Ethernet switch must perform to
process inline power requests made by a link partner (LP) that is, in turn, capable of
receiving inline power.
1. Enable the inline powered device detection mode on each VSC8601 PHY using its
serial management interface. Set register bit 23E.10 to 1.
2. Ensure that the VSC8601 device auto-negotiation enable bit (register 0.12) is also
set to 1. In the application, the device sends a special Fast Link Pulse (FLP) signal
to the LP. Reading register bit 23E.9:8 returns 00 during the search for devices that
require Power-over-Ethernet (PoE).
3. The VSC8601 PHY monitors its inputs for the FLP signal looped back by the LP. An
LP capable of receiving PoE will loopback the FLP pulses when it is in a
powered-down state. This is reported when VSC8601 device register bit 23E.9:8
reads back 01. It can also be verified as an inline power detection interrupt by
Revision 4.1
September 2009
Page 22
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
