11-2
MCF5272 User’s Manual
Module Operation
11.2 Module Operation
The FEC is implemented using a combination of hardware and microcode. Figure 11-1
shows a functional block diagram of this module.
Figure 11-1. Ethernet Block Diagram
Figure 11-2 shows a fast Ethernet module.
Figure 11-2. Fast Ethernet Module Block Diagram
The descriptor controller opens and closes the buffer descriptors. The DMA controller
manages the data transfer. As soon as the DMA channel is initialized, it begins transferring
data. An on-board RAM acts as both a transmit and receive FIFO, and also provides scratch
memory for the FEC.
The RAM is the focal point of all data flow in the FEC. The RAM is divided into three
sections: transmit FIFO, receive FIFO, and descriptor controller memory. User data flows
to or from the DMA unit from or to the receive/transmit FIFOs. Transmit data flows from
the transmit FIFO into the transmit block. Receive data flows from the receive block into
the receive FIFO.
The user controls the FEC by writing into control registers located in each block. The
control and status registers (CSRs) provide global control (for example, Ethernet reset and
enable) and interrupt handling. The MII block provides a serial channel for the FEC and
external physical layer device to pass control and status information.
Internal Bus Interface
Dedicated DMA/
CSRs
RAM
RAM I/F
FIFO
Descriptor
Controller
MII
Receive
Transmit
Bus
Controller
Controller
E_MDC
E_MDIO
E_RxCLK
E_RxDV
E_RxD[3:0]
E_RxER
E_TxCLK
E_TxEN
E_TxD[3:0]
E_TxER
E_CRS,E_COL
Descriptor Access
Содержание DigitalDNA ColdFire MCF5272
Страница 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Страница 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Страница 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Страница 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Страница 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Страница 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Страница 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Страница 338: ...13 44 MCF5272 User s Manual Application Examples ...
Страница 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Страница 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Страница 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Страница 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...
Страница 548: ...INDEX Index 12 MCF5272 User s Manual ...