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S3C2500B
7.3 MAC FUNCTION BLOCKS
The major function blocks of each Ethernet of MAC layer are described in Table 7-1 and Figure 7-1.
Function Block
Media Independent
Interface (MII)
Transmitter block
Receiver block
Flow control block
MAC control (command)
and status registers
Loop-back circuit
7.3.1 MEDIA INDEPENDENT INTERFACE (MII)
Both transmitter and receiver blocks operate using the MII, which was developed by the IEEE802.3 task force on
100-Mbps Ethernet. This interface has the following characteristics:
•
Media independence
•
Multi-vendor points of interoperability
•
Supports connection of MAC layer and physical layer entity (PHY) devices
•
Capable of supporting both 100M-bps and 10M-bps and 1M-bps data rates
•
Data and delimiters are synchronous to clock references
•
Provides independent 4-bit wide transmit and receive data paths
•
Uses TTL signal levels that are compatible with common digital CMOS ASIC processes
•
Supports connection of PHY layer and station management (STA) devices
• •
Provides a simple management interface
• •
Capable of driving a limited length of shielded cable
Table 7-1. MAC Function Block Descriptions
The interface between the physical layer and the transmit/receiver blocks.
Moves the outgoing data from the transmit buffer to the MII. This includes circuits
for generating the CRC, checking parity, and generating preamble or jam.
Also has timers for back-off after collision and the inter-frame gap follows a
transmission.
Accepts incoming data from the MII and stores it in the MRxFIFO. The receiver
block has logic for computing and checking the CRC value, generating parity for
data from the MII, and checking minimum and maximum frame lengths.
Also has a CAM that provides for address lookup, and for acceptance or rejection
for frame based on their destination address.
Recognizes MAC-control frame and supports the pause operation for full-duplex
links. The flow control block also supports generation of pause frame, and
provides timers and counters for pause control.
Controls programmable options, including the enabling or disabling of signals that
notify the system when conditions occur. The status registers hold information for
error handling software, and the error counters accumulate statistical information
for network management software.
Provides for MAC-layer testing in isolation from the MII and physical layer.
ETHERNET CONTROLLER
Description
7-3
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