SNLS779A July 2025 – November 2025 DP83TC815-Q1
PRODUCTION DATA
The Serial Gigabit Media Independent Interface (SGMII) provides a means for data transfer between MAC and PHY with significantly less signal pins (4 pins) compared to MII (14 pins), RMII (7 pins) or RGMII (12 pins). SGMII uses low-voltage differential signaling (LVDS) to reduce emissions and improve signal quality.
The DP83TC815-Q1 SGMII is capable of operating in 4-wire. SGMII is configurable through hardware bootstraps. In 4-wire operation, two differential pairs are used to transmit and receive data. Clock and data recovery are performed in the MAC and in the PHY.
Because the DP83TC815-Q1 operates at 100Mbps, the 1.25-Gbps rate of the SGMII is excessive. The SGMII specification allows for 100Mbps operation by replicating each byte within a frame 10 times. Frame elongation takes place above the IEEE 802.3 PCS layer, which prevents the start-of-frame delimiter from appearing more than once.
The DP83TC815-Q1 only supports 100Mbps speed, therefore SGMII Auto-Negotiation can be disabled by setting bit[0] = 0b0 in the Register 0x608.
The SGMII signals are summarized in Table 7-36.
| FUNCTION | PINS |
|---|---|
| Data Signals | TX_M, TX_P |
| RX_M, RX_P |