LAN8740A Datasheet, PDF (4/136 Pages) Microchip Technology – Small Footprint MII/RMII 10/100 Energy Efficient Ethernet Transceiver with HP Auto-MDIX and flexPWR® Technology

LAN8740A/LAN8740Ai
1.0 INTRODUCTION
1.1 General Terms and Conventions
The following is a list of the general terms used throughout this document:
BYTE
FIFO
MAC
MII
RMII™
N/A
X
RESERVED
SMI
8 bits
First In First Out buffer; often used for elasticity buffer
Media Access Controller
Media Independent Interface
Reduced Media Independent Interface
Not Applicable
Indicates that a logic state is “don’t care” or undefined.
Refers to a reserved bit field or address. Unless otherwise noted, reserved bits must always be zero
for write operations. Unless otherwise noted, values are not guaranteed when reading reserved bits.
Unless otherwise noted, do not read or write to reserved addresses.
Serial Management Interface
1.2 General Description
The LAN8740A/LAN8740Ai is a low-power 10BASE-T/100BASE-TX physical layer (PHY) transceiver with variable I/O
voltage that is compliant with the IEEE 802.3, 802.3u, and 802.3az (Energy Efficient Ethernet) standards. Energy Effi-
cient Ethernet (EEE) support results in significant power savings during low link utilizations.
The LAN8740A/LAN8740Ai supports communication with an Ethernet MAC via a standard MII (IEEE 802.3u)/RMII inter-
face. It contains a full-duplex 10-BASE-T/100BASE-TX transceiver and supports 10 Mbps (10BASE-T) and 100 Mbps
(100BASE-TX) operation. The LAN8740A/LAN8740Ai implements auto-negotiation to automatically determine the best
possible speed and duplex mode of operation. HP Auto-MDIX support allows the use of direct connect or cross-over
LAN cables. Integrated Wake on LAN (WoL) support provides a mechanism to trigger an interrupt upon reception of a
perfect DA, broadcast, magic packet, or wakeup frame.
The LAN8740A/LAN8740Ai supports both IEEE 802.3-2005 compliant and vendor-specific register functions. However,
no register access is required for operation. The initial configuration may be selected via the configuration pins as
described in Section 3.7, "Configuration Straps". Register-selectable configuration options may be used to further define
the functionality of the transceiver.
The LAN8740A/LAN8740Ai can be programmed to support wake-on-LAN at the physical layer, allowing detection of
configurable Wake-up Frame and Magic packets. This feature allows filtering of packets at the PHY layer, without requir-
ing MAC intervention. Additionally, the LAN8740A/LAN8740Ai supports cable diagnostics which allow the device to
identify opens/shorts and their location on the cable via vendor-specific registers.
Per IEEE 802.3-2005 standards, all digital interface pins are tolerant to 3.6 V. The device can be configured to operate
on a single 3.3 V supply utilizing an integrated 3.3 V to 1.2 V linear regulator. The linear regulator may be optionally
disabled, allowing usage of a high efficiency external regulator for lower system power dissipation.
DS00001987A-page 4
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