Ethernet Functional Description: Mac 802.3 - STMicroelectronics STM32F405 Reference Manual

RM0090
33.5

Ethernet functional description: MAC 802.3

The IEEE 802.3 International Standard for local area networks (LANs) employs the
CSMA/CD (carrier sense multiple access with collision detection) as the access method.
The Ethernet peripheral consists of a MAC 802.3 (media access control) controller with
media independent interface (MII) and a dedicated DMA controller.
The MAC block implements the LAN CSMA/CD sublayer for the following families of
systems: 10 Mbit/s and 100 Mbit/s of data rates for baseband and broadband systems. Half-
and full-duplex operation modes are supported. The collision detection access method is
applied only to the half-duplex operation mode. The MAC control frame sublayer is
supported.
The MAC sublayer performs the following functions associated with a data link control
procedure:
•
Data encapsulation (transmit and receive)
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•
Media access management
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Basically there are two operating modes of the MAC sublayer:
•
Half-duplex mode: the stations contend for the use of the physical medium, using the
CSMA/CD algorithms.
• Full duplex mode: simultaneous transmission and reception without contention
resolution (CSMA/CD algorithm are unnecessary) when all the following conditions are
met:
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33.5.1 MAC 802.3 frame format
The MAC block implements the MAC sublayer and the optional MAC control sublayer
(10/100 Mbit/s) as specified by the IEEE 802.3-2002 standard.
Two frame formats are specified for data communication systems using the CSMA/CD
MAC:
•
Basic MAC frame format
•
Tagged MAC frame format (extension of the basic MAC frame format)
Ethernet (ETH): media access control (MAC) with DMA controller
Framing (frame boundary delimitation, frame synchronization)
Addressing (handling of source and destination addresses)
Error detection
Medium allocation (collision avoidance)
Contention resolution (collision handling)
physical medium capability to support simultaneous transmission and reception
exactly 2 stations connected to the LAN
both stations configured for full-duplex operation
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