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60x-Bus
Peripheral Bus
RX_ER
Receiver
RX_DV
COL
CRS
RXD[3Ð0]
30.2 Features
The following is a list of Fast Ethernet key features:
¥ Support for Fast Ethernet through the MII (media-independent interface)
¥ Performs MAC (media access control) layer functions of Fast Ethernet and IEEE
802.3x
¥ Performs framing functions
Ñ Preamble generation and stripping
Ñ Destination address checking
Ñ CRC generation and checking
Ñ Automatic padding of short frames on transmit
Ñ Framing error (dribbling bits) handling
¥ Full collision support
Ñ Enforces the collision (jamming and TX_ER assertion)
Ñ Truncated binary exponential backoff algorithm for random wait
Ñ Two nonaggressive backoff modes
Ñ Automatic frame retransmission (until retry limit is reached)
Ñ Automatic discard of incoming collided frames
Ñ Delay transmission of new frames for speciÞed interframe gap
¥ Bit rates up to 100 Mbps
¥ Receives back-to-back frames
¥ Detection of receive frames that are too long
MOTOROLA
Control
Registers
Receive
Control
Data
UNIT
FIFO
Shifter
Figure 30-2. Ethernet Block Diagram
Chapter 30. Fast Ethernet Controller
Part IV. Communications Processor Module
Internal Clocks
Transmit
Transmitter
Data
Control
FIFO
Unit
TXD[3Ð0]
Shifter
Slot Time
And Defer
Counter
RX_CLK
Clock
Generator
TX_CLK
TX_ER
TX_EN
COL
CRS
30-3
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