88e3015 Marvell Semiconductor, Inc., 88e3015 Datasheet - Page 41

• Manufacturer Part Number: 88e3015
• Description: Integrated 10/100 Fast Ethernet Transceiver
• Manufacturer: Marvell Semiconductor, Inc.

2.11 LED Interface
The LEDs can either be controlled by the PHY or controlled externally, independent of the state of the PHY.
2.11.1 Manual Override
External control is achieved by writing to the PHY Manual LED Override register 25.5:0. Any of the LEDs can be
turned on, off, or made to blink at variable rates independent of the state of the PHY. This independence elimi-
nates the need for driving LEDs from the MAC or the CPU. If the LEDs are driven from the CPU located at the
back of the board, the LED lines crossing the entire board will pick up noise. This noise will cause EMI issues.
Also, PCB layout will be more difficult due to the additional lines routed across the board.
When the LEDs are controlled by the PHY, the activity of the LEDs is determined by the state of the PHY. Each
LED can be programmed to indicate various PHY states, with variable blink rate.
Any one of the LEDs can be controlled independently of the other LEDs (i.e one LED can be externally controlled
while another LED can be controlled by the state of the PHY).
Table 22:
Copyright © 2006 Marvell
October 26, 2006, Advance
B i ts
25.5:4
25.3:2
25.1:0
Manual Override
F ie l d
ForceLED2
ForceLED1
ForceLED0
D e s c r i p t i o n
00 = Normal
01 = Blink[1]
10 = LED Off
11 = LED On
00 = Normal
01 = Blink
10 = LED Off
11 = LED On
00 = Normal
01 = Blink
10 = LED Off
11 = LED On
Document Classification: Proprietary Information
CONFIDENTIAL
Doc. No. MV-S103657-00, Rev. C
LED Interface
Page 41