lan8720 Standard Microsystems Corp., lan8720 Datasheet - Page 18

• Manufacturer Part Number: lan8720
• Description: Small Footprint Rmii 10/100 Ethernet Transceiver With Hp Auto-mdix Support
• Manufacturer: Standard Microsystems Corp.

Revision 1.0 (04-15-09)
Chapter 4 Architecture Details
4.1
4.2
4.2.1
MAC
Functionally, the transceiver can be divided into the following sections:
The data path of the 100Base-TX is shown in
100M Transmit Data Across the MII/RMII Interface
For MII, the MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate
valid data. The data is latched by the transceiver’s MII block on the rising edge of TXCLK. The data
is in the form of 4-bit wide 25MHz data.
For RMII, the MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate
valid data. The data is latched by the transceiver’s RMII block on the rising edge of REF_CLK. The
data is in the form of 2-bit wide 50MHz data.
Top Level Functional Architecture
100Base-TX Transmit
125 Mbps Serial
100Base-TX transmit and receive
10Base-T transmit and receive
RMII interface to the controller
Auto-negotiation to automatically determine the best speed and duplex possible
Management Control to read status registers and write control registers
RMII 50Mhz by 2 bits
Ref_CLK
Converter
MLT-3
NRZI
Figure 4.1 100Base-TX Data Path
Magnetics
DATASHEET
RMII
NRZI
18
Converter
PLL
by 4 bits
MLT-3
25MHz
Figure
MLT-3
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
4.1. Each major block is explained below.
Encoder
4B/5B
MLT-3
RJ45
25MHz by
Driver
5 bits
Tx
MLT-3
SMSC LAN8720/LAN8720i
Scrambler
and PISO
CAT-5
Datasheet