VSC8601 Datasheet
Functional Descriptions
3.12
LED Interface
The VSC8601 device drives up to three LEDs directly. All LED outputs are active-low
and are driven using 3.3 V from the VDD33 power supply. When active, the pins are
mainly used to sink current of the cathode side of an LED, but the pins can also supply
source power to the anode portion of LEDs when they are not in the active state. This
allows for two LED pins to be used to drive a multi-status, bi-colored LED.
3.12.1
Simple or Enhanced LED Method
The VSC8601 provides two methods for controlling its LEDs: simple or enhanced. The
simple LED method is backward-compatible to the LED control found in prior Vitesse
Ethernet PHY devices. The simple LED method eases software backward compatibility
for customers switching to the VSC8601. The simple LED method is controlled by MII
Register 27 and is enabled by default.
For added flexibility, the VSC8601 LED can be controlled using the enhanced LED
method. The enhanced LED method is enabled by setting MII Register 17E.4 = 1. When
enabled, then the LEDs are controlled by MII Registers 16E and 17E. In this method,
the MII Register 27 settings are ignored.
Simple LED Method When MII Register 17E.4 = 0, the LEDs are controlled by the
simple LED method. This LED method is enabled on power-up and is controlled by MII
Register 27. In this method, MII Register 27 controls the LEDs. For more information,
see “LED Control,” page 52.
Enhanced LED Method When MII Register 17E.4 = 1, the LEDs are controlled by the
enhanced LED method. In this method, MII Register 16E and 17E control the LEDs. For
more information, see “Enhanced LED Method Select,” page 56 and “Enhanced LED
Behavior,” page 57.
3.12.2
LED Modes
If you are using the enhanced LED method, there are several LED modes available.
They are found in MII Register 16E. Each LED pin can be configured to display different
status information. Set the LED mode either by using register 16E or with the CMODE
pin setting. The following table summarizes the LED functions.
Note The modes listed in the following table are equivalent to the setting used in
register 16E to configure each LED pin. For the LED states listed, 1 = pin held high
(de-asserted), 0 = pin held low (asserted), and blink/pulse-stretch is dependent on the
LED behavior setting in register 17E.
Table 3.
LED Mode and Function Summary
Mode
Function Name
LED State and Description
0
Link/activity
1 = No link in any speed on any media interface.
0 = Valid link at any speed on any media interface.
Blink or pulse-stretch = Valid link at any speed on any media interface and
with activity present.
1
Link1000/activity
1 = No link in 1000BASE-T.
0 = Valid 1000BASE-T link.
Blink or pulse-stretch = Valid 1000BASE-T link with activity present.
Revision 4.1
September 2009
Page 28
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
