3.4.1.1 Ethernet 10/100 Interface

The KSZ8081 is a single-supply 10Base-T/100Base-TX Ethernet physical-layer transceiver for transmission and reception of data over a standard CAT-5 unshielded twisted pair (UTP) cable. The KSZ8081 is a highly-integrated PHY solution. It reduces board cost and simplifies board layout by using on-chip termination resistors for the differential pairs and by integrating a low-noise regulator to supply the 1.2V core, and by offering 1.8/2.5/3.3V digital I/O interface support.

The KSZ8081RNA is connected over the Reduced Media Independent Interface (RMII) directly to the RMII-compliant MAC inside the SAMA7G5 MPU. As the power-up default, the KSZ8081RNA uses a 25 MHz MEMS oscillator to generate all required clocks, including the 50-MHz RMII reference clock output for the MAC.

For more information about the KSZ8081RNx, refer to the product web page.

An indiviual unique 48-bit MAC address (Ethernet hardware address) is allocated to this product and is stored in one of the Microchip 24AA025E48 TWI serial EEPROMs described in Dual Serial EEPROM.

Additionally, for monitoring and control purposes, the RJ45 connectors feature a LED functionality to indicate activity, link, and speed status.

Figure 3-31. RMII Ethernet Interface Schematic
Table 3-18. Ethernet PHY 10/100 Signal Descriptions
PIOSignal NameShared WithSignal Description
PD21ETH1_TXEN_PD21RPi 40-pin connectorTransmit enable or RPi connector GPIO
PD22ETH1_TW1_TW0_PD22PDM microphoneTransmit data line 0 or PDM clock line
PD23ETH1_TX1_PD23PDM microphoneTransmit data line 1 or PDM data line 0
PD24ETH1_CRSDV_PD24PDM microphoneReceive data valid or carrier sense and data valid or PDM data line 1
PD25ETH1_RX0_PD25RPi 40-pin connectorReceive data line 0 or RPi connector GPIO
PD26ETH1_RX1_PD26RPi 40-pin connectorReceive data line 1 or RPi connector GPIO
PD27ETH1_RXER_PD27RPi 40-pin connectorReceive error or RPi connector GPIO
PD28ETH1_MDC_PD28RPi 40-pin connectorManagement data clock or RPi connector GPIO
PD29ETH1_MDIO_PD29RPi 40-pin connectorManagement data input/output or RPi connector GPIO
PD30ETH1_TXCK_PD30RPi 40-pin connectorTransmit clock or 50 MHz reference clock or RPi connector GPIO
PA21ETH1_INT_PA21 --Ethernet 1 interrupt
Table 3-19. Ethernet RJ45 Connector J6 Pin Assignment
Pin No.Signal NameSignal Description
1TCTDecoupling capacitor
2ETH1_TX_PPhysical transmit or receive signal (+ differential)
3ETH1_TX_NPhysical transmit or receive signal (- differential)
4ETH1_RX_PPhysical receive or transmit signal (+ differential)
5RCTDecoupling capacitor
6ETH1_RX_NPhysical receive or transmit signal (- differential)
7NCGreen LED cathode
8NCGreen LED anode
9ETH1_LEDYellow LED cathode
10Yellow LED anode
11EarthEarth ground
12EarthEarth ground