I have query regarding PCB design layout of Raspberry Pi (RPI). I wanted to know how LAN9512 chip is connected to Ethernet RJ45.

I found one of PCB layout picture which suggests there is line on PCB which goes from LAN9512 chip to Ethernet RJ45 which I guess mark as R23.

What does R23 represent in PCB design, is it some kind of system bus or USB bus?

Same way how CPU/GPU is connected to component like D2 & D3 (RAM)?

Raspberry Pi Board

(Original Image)

Raspberry Pi Front

(Original Image)

PS: I'm not at all familiar with PCB design.


R23, and other components marked Rxx, are resistors. The Ethernet connector is at the right of that page, and is marked "P2", and includes inductors, transformers and resistors inside the connector assembly.

There are four wires from the 9512 to the ethernet connector. Those wires each have a resistor to +3.3 volts, and a small capacitor (C22 - C25) to ground.

The labels R23, C22, P4 and similar are called "reference designators". The letter indicates the type of part, and the number identifies the particular part on the schematic, PC board and parts list.


There are two LVDS pairs, one TX and one RX, between the RJ45 and the LAN chip. From the RPI schematic (pdf), copied below:

enter image description here

The RJ45 is the connector on the right, the LAN chip is on the left.

  • \$\begingroup\$ Thanks @Stacey for the this particular Diagram.I am somewhat weak in electronic so I have to go through all components to get my understanding going. \$\endgroup\$ – Amit Singh Tomar May 27 '14 at 16:24

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