GMII Protocolos compatibles

Computadoras y servidores

Gigabit Media Independent Interface

¿Qué es 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 Referencia 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 compatibles con GMII

Serie TravelLogic

Serie TravelLogic
Serie LA4000

Serie LA4000

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¿Cómo analizar GMII con instrumentos Acute

1

Conecte su analizador lógico Acute a las señales GMII: TXD[7:0], GTX_CLK, TX_EN, TX_ER, RXD[7:0], RX_CLK, RX_DV y RX_ER.

2

Conecte un cable de tierra a la referencia de tierra de la placa objetivo.

3

En el software Acute, seleccione el GMII protocol decoder y asigne cada señal al canal de entrada correspondiente.

4

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

5

Capture y visualice los Ethernet frames for both directions, verifying payload integrity and FCS validation.

Preguntas frecuentes

Que tasa de muestreo necesito para el análisis 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 mi decodificador GMII muestra errores de FCS en las tramas recibidas?
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.
Cuantos canales se necesitan para el análisis 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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