Texas Instruments TMS320DM646x MAC Receiver, Receive Address, Transmit DMA Engine, Transmit Fifo

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Architecture

2.8.1.3MAC Receiver

The MAC receiver detects and processes incoming network frames, de-frames them, and puts them into the receive FIFO. The MAC receiver also detects errors and passes statistics to the statistics RAM.

2.8.1.4Receive Address

This sub-module performs address matching and address filtering based on the incoming packet’s destination address. It contains a 32-by-53 bit two-port RAM, in which up to 32 addresses can be stored to be either matched or filtered by the EMAC. The RAM may contain multicast packet addresses, but the associated channel must have the unicast enable bit set, even though it is a multicast address. The unicast enable bits are used with multicast addresses in the receive address RAM (not the multicast hash enable bits). Therefore, hash matches can be disabled, but specific multicast addresses can be matched (or filtered) in the RAM. If a multicast packet hash matches, the packet may still be filtered in the RAM. Each packet can be sent to only a single channel.

2.8.1.5Transmit DMA Engine

The transmit DMA engine is the interface between the transmit FIFO and the CPU. It interfaces to the CPU through the bus arbiter in the EMAC control module.

2.8.1.6Transmit FIFO

The transmit FIFO consists of 24 cells of 64 bytes each and associated control logic. This enables a packet of 1518 bytes (standard Ethernet packet size) to be sent without the possibility of underrun. The FIFO buffers data in preparation for transmission.

2.8.1.7MAC Transmitter

The MAC transmitter formats frame data from the transmit FIFO and transmits the data using the CSMA/CD access protocol. The frame CRC can be automatically appended, if required. The MAC transmitter also detects transmission errors and passes statistics to the statistics registers.

2.8.1.8Statistics Logic

The Ethernet statistics are counted and stored in the statistics logic RAM. This statistics RAM keeps track of 36 different Ethernet packet statistics.

2.8.1.9State RAM

State RAM contains the head descriptor pointers and completion pointers registers for both transmit and receive channels.

2.8.1.10EMAC Interrupt Controller

The interrupt controller contains the interrupt related registers and logic. The 18 raw EMAC interrupts are input to this submodule and masked module interrupts are output.

2.8.1.11Control Registers and Logic

The EMAC is controlled by a set of memory-mapped registers. The control logic also signals transmit, receive, and status related interrupts to the CPU through the EMAC control module.

2.8.1.12Clock and Reset Logic

The clock and reset submodule generates all the EMAC clocks and resets. For more details on reset capabilities, see Section 2.14.1.

SPRUEQ6–December 2007 Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO) 39

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