Ethernet

Pin Signal type I/O Remarks
19 ENET_RST 3V3 OUT  
20 ENET_CLK125 3V3 IN  
21 ENET_INT 3V3 IN  
22 ENET_MDIO 3V3 I/O  
23 ENET_MDC 3V3 OUT  
24 ENET_RXC 3V3 I/O  
25 ENET_RXCTL 3V3 I/O RMII:CRS_DV
26 ENET_RD0 3V3 I/O RMII:RXD0
27 ENET_RD1 3V3 I/O RMII:RXD1
28 ENET_RD2 3V3 IN  
29 ENET_RD3 3V3 I/O  
30 ENET_TXCTL 3V3 I/O RMII:TX_EN
31 ENET_TXC 3V3 I/O  
32 ENET_TD3 3V3 IN  
33 ENET_TD2 3V3 I/O  
34 ENET_TD1 3V3 I/O RMII:TXD1
35 ENET_TD0 3V3 I/O RMII:TXD0

Wiring example

RGMII Timing (KSZ9031RNX Gigabit Ethernet PHY)

As the default, after power-up or reset, the KSZ9031RNX RGMII timing conforms to the timing requirements in the RGMII Version 2.0 Specification for internal PHY chip delay.

For the transmit path (MAC to KSZ9031RNX), the KSZ9031RNX does not add any delay locally at its GTX_CLK, TX_EN and TXD[3:0] input pins, and expects the GTX_CLK delay to be provided on-chip by the MAC. If MAC does not provide any delay or insufficient delay for the GTX_CLK, the KSZ9031RNX has pad skew registers that can provide up to 1.38ns on-chip delay.

For the receive path (KSZ9031RNX to MAC), the KSZ9031RNX adds 1.2ns typical delay to the RX_CLK output pin with respect to RX_DV and RXD[3:0] output pins. If necessary, the KSZ9031RNX has pad skew registers that can adjust the RX_CLK on-chip delay up to 2.58ns from the 1.2ns default delay.

It is common to implement RGMII PHY-to-MAC designs that either PHY, MAC, or both PHY and MAC are not fully RGMII v2.0 compliant with on-chip clock delay. These combinations of mixed RGMII v1.3/v2.0 designs and plus sometimes non-matching RGMII PCB trace routings require a review of the entire RGMII system timings (PHY on-chip, PCB trace delay, MAC on-chip) to compute the aggregate clock delay and determine if the clock delay timing is met. If timing adjustment is needed, pad skew registers are provided by the KSZ9031RNX. Refer to RGMII Pad Skew Registers section.

RGMII v2.0 Specification

Parameter MIN TYP MAX
Data to clock output skew (at transmitter) per RGMII v1.3 (external delay) -500ps   500 ps
Data to clock input skew (at receiver) per RGMII v1.3 (external delay) 1 ns   2.6 ns
Data to clock output setup (at transmitter – integrated delay) 1.2 ns 2ns  
Data to clock output setup (at transmitter – integrated delay) 1.2 ns 2ns  

The RGMII Version 2.0 Specification defines the RGMII data-to-clock skews only for 1000Mbps operation, which usesboth clock edges for sampling the data and control signals at the 125MHz clock frequency (8ns period). For 10/100Mbps operations, the data signals are sampled on the rising clock edge and the control signals are sampled on both clock edges. With slower clock frequencies, 2.5MHz (400ns period) for 10Mbps and 25MHz (40ns period) for 100Mbps, the RGMII data-to-clock skews for 10/100Mbps operations will have greater timing margins than for 1000Mbps operation, and therefore can be relaxed from 2.6ns (maximum) for 1000Mbps to 160ns (maximum) for 10Mbps and 16ns (maximum) for 100Mbps

See also

Microchip KSZ9031RNX datasheet

Microchip AN-111 General PCB Design and Layout Guidelines

QS Standard Contact Group Index

Pins Funktion Pins Funktion Pins Funktion Pins Funktion
1-4 SPI 5-10 I2C 11-14 CAN 15-18 SAI
19-35 Ethernet 36-42 SD Interface 43-48 USB 49-52 Power Supply, Reset and Boot mode
53-76 18-bit RGB Display Interface 77-78 Backlight and Display Control 53-72 Camera 79-88 MIPI DSI Display
89-96 UART 97-100 SPI 1A,75A,76A,100A PCIe 25A,26A,50A,51A USB3 Super Speed