LAN9313 Datasheet, PDF (86/398 Pages) SMSC Corporation – Three Port 10/100 Managed Ethernet Switch with MII

7.2.1
Three Port 10/100 Managed Ethernet Switch with MII
Datasheet
100BASE-TX Transmit
The 100BASE-TX transmit data path is shown in Figure 7.2. Shaded blocks are those which are
internal to the PHY. Each major block is explained in the following sections.
Port x
MAC
Internal
MII Transmit Clock
100M
PLL
Internal
MII 25 MHz by 4 bits
MII MAC
Interface
25MHz
by 4 bits
4B/5B
Encoder
25MHz by
5 bits
Scrambler
and PISO
NRZI
Converter
NRZI
MLT-3
Converter
125 Mbps Serial
MLT-3
100M
TX Driver
MLT-3
Magnetics
MLT-3
RJ45
MLT-3
CAT-5
7.2.1.1
7.2.1.2
Figure 7.2 100BASE-TX Transmit Data Path
MII MAC Interface
For a transmission, the switch fabric MAC drives the transmit data to the PHYs MII MAC Interface.
The MII MAC Interface is described in detail in Section 7.2.7, "MII MAC Interface".
Note: The PHY is connected to the switch fabric MAC via standard MII signals. Refer to the IEEE
802.3 specification for additional details.
4B/5B Encoder
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 7.2. 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.
Revision 1.2 (04-08-08)
86
DATASHEET
SMSC LAN9313/LAN9313i