LAN9420 Datasheet, PDF (65/171 Pages) SMSC Corporation – Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
„ Energy detect
„ Duplex, link activity and speed indicator LEDs
„ Minimal external components are required for the utilization of the integrated PHY
Functionally, the PHY can be divided into the following sections:
„ 100BASE-TX transmit and receive
„ 10BASE-T transmit and receive
„ Internal MII interface to the Ethernet Media Access Controller (MAC)
„ Auto-negotiation to automatically determine the best speed and duplex possible
„ Management Control to read status registers and write control registers
MAC
TX_CLK
100M
PLL
Internal
MII 25 MHz by 4 bits
MII
25MHz 4B/5B 25MHz by Scrambler
by 4 bits _Encoder 5 bits _{and PISO}
NRZI
Converter
NRZI
125 Mbps Serial
MLT-3
Tx
Converter ^MLT-3 Driver
MLT-3
MLT-3 Magnetics
3.6.1
3.6.1.1
RJ45
MLT-3
CAT-5
Figure 3.25 100BASE-TX Data Path
100BASE-TX Transmit
The data path of the 100BASE-TX is shown in Figure 3.25. Each major block is explained below.
4B/5B Encoding
The transmit data passes from the MII block to the 4B/5B encoder. This block encodes the data from
4-bit nibbles to 5-bit symbols (known as “code-groups”) according to Table 3.21. Each 4-bit data-nibble
is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used for
control information or are not valid.
The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles,
0 through F. The remaining code-groups are given letter designations with slashes on either side. For
example, an IDLE code-group is /I/, a transmit error code-group is /H/, etc.
The encoding process may be bypassed by clearing bit 6 of register 31. When the encoding is
bypassed, the 5^th transmit data bit is equivalent to TX_ER.
SMSC LAN9420/LAN9420i
65
DATASHEET
Revision 1.6 (07-18-11)