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MII/RMII selection
When the Ethernet controller is not in reset mode or the clock is enabled, the
application program needs to set MII/RMII mode.
Media access control (MAC 802.3)
The access method of IEEE 802.3 international standard applicable to LAN is
CSMA/CD. The Ethernet peripheral consists of one MAC 802.3 controller with
MII and a dedicated DMA controller.
The following system uses LAN CSMA/CD sublayer
Support half-duplex and full-duplex
The conflict detection access method is applicable only to half-duplex
The data rate of baseband system and broadband system is 10 Mbit/s
and 100Mbit/s
Support MAC to control frame sublayer
Functions of MAC sublayer
Data encapsulation
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Framing
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Addressing
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Error detection
Media access management
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Media distribution
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Contention resolution
Working mode of MAC sublayer
Half-duplex: Contention for physical media with CSMA/CD algorithm
Full duplex: When the physical media supports synchronous
transmission and receiving, and two full-duplex stations are
connected to the LAN, data can be transmitted and received at the
same time without solving the contention problem.
MAC 802.3 frame format
IEEE 802.3-2002 standard specifies MAC uses MAC sublayer and optional
MAC control sublayer (10/100 Mbit/s).
Two frame formats are specified for data communication system using
CSMA/CD MAC
Basic MAC frame format
Tagged MAC frame format
Frame structure of field
Header: 7 bytes, used for synchronization
Start frame delimiter: 1 byte, indicating the start of the frame
Destination address and source address: MAC address field (6
bytes), indicating the address of destination station and source station