This is a single-width PMOD module with the RMII DP83TC813 100BASE-T1 PHY.
100BASE-T1 require one of the device to be setup as a Slave, and the other one as a Master. This concept doesn't exist in 100BASE-T and most usual Ethernet types, and seems to be a particularity of 100BASE-T1 and 1000BASE-T1. Check R42 placement to setup Master/Slave mode.
Straps have been setup for RMII slave mode (refclk has to be supplied from the host at 50MHz), 100BASE-T1 Master Mode (R43 present) and MDIO PHYADD=0 (JP1 and JP2 open).
When R42 is placed, the DP83TC813 acts as a Master. When R42 isn't placed, the internal pulldown of the PHY enables the Slave mode.
MDIO PHY address is set with JP1 and JP2. 9 different addresses can be configured:
| JP1 | JP2 | PHYADD[0-1] | PHYADD[2-3] | PHYADD |
|---|---|---|---|---|
| OPEN | OPEN | 0b00 | 0b00 | 0b0000 |
| 1-2 | OPEN | 0b11 | 0b00 | 0b0011 |
| 2-3 | OPEN | 0b01 | 0b00 | 0b0001 |
| OPEN | 1-2 | 0b00 | 0b11 | 0b1100 |
| 1-2 | 1-2 | 0b11 | 0b11 | 0b1111 |
| 2-3 | 1-2 | 0b01 | 0b11 | 0b1101 |
| OPEN | 2-3 | 0b00 | 0b01 | 0b0100 |
| 1-2 | 2-3 | 0b11 | 0b01 | 0b0111 |
| 2-3 | 2-3 | 0b01 | 0b01 | 0b0101 |
| Pin | type | Function | Description |
|---|---|---|---|
| 1 | I | TX_D1 | Transmit Data |
| 2 | I | TXEN | Transmit Enable |
| 3 | O | RX_D0 | Receive Data |
| 4 | I | REFCLK | 50MHz clock |
| 5 | GND | ||
| 6 | VCC | 3.3V rail | |
| 7 | I | TX_D0 | Transmit Data |
| 8 | O | RX_DV | Receive / Data valid |
| 9 | O | RX_D1 | Receive Data |
| 10 | I, PU | RST_T1 | Reset |
| 11 | GND | ||
| 12 | VCC | 3.3V rail |
Legend:
- I: input (ie. output from the host)
- O: output (ie. input from the host)
- PU: Pull-up