LAN8720A-CP-TR SMSC, LAN8720A-CP-TR Datasheet - Page 24
![no-image](/images/manufacturer_photos/0/6/617/smsc_sml.jpg)
LAN8720A-CP-TR
Manufacturer Part Number
LAN8720A-CP-TR
Description
Ethernet ICs RMII 10/100 ETH XCVR w/HP AutoMDIXSupport
Manufacturer
SMSC
Datasheet
1.LAN8720A-CP.pdf
(79 pages)
Specifications of LAN8720A-CP-TR
Product
Ethernet Transceivers
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LAN8720A-CP-TR
Manufacturer:
MORNSUN
Quantity:
1 000
Part Number:
LAN8720A-CP-TR
Manufacturer:
SMSC
Quantity:
20 000
Revision 1.2 (11-10-10)
3.2
The purpose of the auto-negotiation function is to automatically configure the transceiver to the
optimum link parameters based on the capabilities of its link partner. Auto-negotiation is a mechanism
for exchanging configuration information between two link-partners and automatically selecting the
highest performance mode of operation supported by both sides. Auto-negotiation is fully defined in
clause 28 of the IEEE 802.3 specification.
Once auto-negotiation has completed, information about the resolved link can be passed back to the
controller via the Serial Management Interface (SMI). The results of the negotiation process are
reflected in the
Negotiation Link Partner Ability
activity and proceeds independently of the MAC controller.
The advertised capabilities of the transceiver are stored in the
Register. The default advertised by the transceiver is determined by user-defined on-chip signal
options.
The following blocks are activated during an Auto-negotiation session:
When enabled, auto-negotiation is started by the occurrence of one of the following events:
On detection of one of these events, the transceiver begins auto-negotiation by transmitting bursts of
Fast Link Pulses (FLP), which are bursts of link pulses from the 10M transmitter. They are shaped as
Normal Link Pulses and can pass uncorrupted down CAT-3 or CAT-5 cable. A Fast Link Pulse Burst
consists of up to 33 pulses. The 17 odd-numbered pulses, which are always present, frame the FLP
burst. The 16 even-numbered pulses, which may be present or absent, contain the data word being
transmitted. Presence of a data pulse represents a “1”, while absence represents a “0”.
The data transmitted by an FLP burst is known as a “Link Code Word.” These are defined fully in IEEE
802.3 clause 28. In summary, the transceiver advertises 802.3 compliance in its selector field (the first
5 bits of the Link Code Word). It advertises its technology ability according to the bits set in the
Negotiation Advertisement
There are 4 possible matches of the technology abilities. In the order of priority these are:
If the full capabilities of the transceiver are advertised (100M, Full Duplex), and if the link partner is
capable of 10M and 100M, then auto-negotiation selects 100M as the highest performance mode. If
Auto-negotiation
Auto-negotiation (digital)
100M ADC (analog)
100M PLL (analog)
100M equalizer/BLW/clock recovery (DSP)
10M SQUELCH (analog)
10M PLL (analog)
10M Transmitter (analog)
Hardware reset
Software reset
Power-down reset
Link status down
Setting the
100M Full Duplex (Highest Priority)
100M Half Duplex
10M Full Duplex
10M Half Duplex (Lowest Priority)
Restart Auto-Negotiate
Speed Indication
Register.
bits of the
Register. The auto-negotiation protocol is a purely physical layer
DATASHEET
bit of the
24
PHY Special Control/Status
Basic Control Register
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Auto Negotiation Advertisement
Register, as well as in the
SMSC LAN8720A/LAN8720Ai
Datasheet
Auto
Auto