Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Chapter 4 Architecture Details
4.1
Top Level Functional Architecture
Functionally, the transceiver can be divided into the following sections:
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
PLL
MAC
Ref_CLK
4B/5B
Encoder
Scrambler
and PISO
25MHz
by 4 bits
25MHz by
5 bits
RMII 50Mhz by 2 bits
RMII
NRZI
Converter
MLT-3
Converter
Tx
Driver
125 Mbps Serial
NRZI
MLT-3
MLT-3
MLT-3
MLT-3
Magnetics
RJ45
CAT-5
Figure 4.1 100Base-TX Data Path
4.2
100Base-TX Transmit
The data path of the 100Base-TX is shown in Figure 4.1. Each major block is explained below.
4.2.1
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.
Revision 1.0 (05-28-09)
SMSC LAN8720/LAN8720i
DATA1S8HEET
SMSC [ SMSC CORPORATION ]
