GMII Protocolos suportados

Computadores e servidores

Gigabit Media Independent Interface

O que é GMII?

GMII (Gigabit Media Independent Interface) is the original 8-bit-wide parallel interface for Gigabit Ethernet MAC-to-PHY connections, defined in IEEE 802.3z. GMII uses separate 8-bit transmit and receive data buses clocked at 125 MHz, providing 1 Gbps throughput without requiring DDR signaling. While RGMII has largely replaced GMII in new designs due to its lower pin count, GMII is still found in FPGA-based Ethernet implementations, network equipment, and legacy designs where the wider bus and simpler SDR timing are advantageous. Engineers working with GMII need to verify data bus timing, clock relationships, and frame integrity at the MAC-PHY boundary.

GMII Referência rápida

type Parallel
signals TXD[7:0], RXD[7:0], GTX_CLK, RX_CLK, etc.
max Speed 125 MHz (1 Gbps)
voltage Range 2.5V
standard IEEE 802.3z

Instrumentos Acute compatíveis com GMII

Série TravelLogic

Série TravelLogic
Série LA4000

Série LA4000

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Como analisar GMII com instrumentos Acute

1

Conecte seu analisador lógico Acute aos sinais GMII: TXD[7:0], GTX_CLK, TX_EN, TX_ER, RXD[7:0], RX_CLK, RX_DV e RX_ER.

2

Conecte um fio terra a referência de terra da placa alvo.

3

No software Acute, selecione o GMII protocol decoder e atribua cada sinal ao canal de entrada correspondente.

4

Configure os parametros esperados de Ethernet speed (10, 100, or 1000 Mbps).

5

Capture e visualize os Ethernet frames for both directions, verifying payload integrity and FCS validation.

Perguntas frequentes

Qual taxa de amostragem e necessária para a análise GMII ?
GMII at 1 Gbps uses a 125 MHz clock with SDR (single data rate) signaling. Sample at a minimum of 500 MHz (4x the clock) for reliable data capture. For timing margin analysis, 1 GHz or higher is recommended. At lower Ethernet speeds (10/100 Mbps), the clock rates are proportionally slower and sample rate requirements are reduced accordingly.
Por que meu decodificador GMII mostra erros de FCS nos quadros recebidos?
FCS errors often indicate a data bit assignment error — with 8 data lines, it is easy to swap bit positions, which produces valid-looking frames with incorrect CRC. Double-check that TXD[0] through TXD[7] and RXD[0] through RXD[7] are each assigned to the correct logic analyzer channels in the proper bit order. Also verify the clock-to-data sampling edge and that the voltage threshold is appropriate.
Quantos canais são necessários para a análise de GMII ?
Full bidirectional GMII requires 22 channels: TXD[7:0], GTX_CLK, TX_EN, TX_ER (11 TX), RXD[7:0], RX_CLK, RX_DV, RX_ER (11 RX). For unidirectional monitoring, 11 channels suffice. This high channel count makes the LA4000 series the recommended instrument for GMII analysis. Adding MDIO (2 channels) brings the total to 24.

Protocolos relacionados

MII RGMII SGMII

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