SNLS742A September 2023 – April 2024 DP83TC811-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 or 6 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 DP83TC811SWRHA-Q1 SGMII is capable of operating in either 4-wire or 6-wire mode. Only 4-wire SGMII is configurable through hardware bootstraps. To enable 6-wire SGMII, bit[14] in the Section 7.6.32 must be set. 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. If the MAC is not capable of recovering the clock from the receive data stream, 6-wire operation can be enabled to output a differential clock that is synchronous with receive data.
Because the DP83TC811SWRHA-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.
Because the DP83TC811SWRHA-Q1 only supports 100Mbps speed, SGMII Auto-Negotitation can be disabled by setting bit[13] = 0b0 in the Section 7.6.6.
The SGMII signals are summarized in Table 7-14.
FUNCTION | PINS |
---|---|
Data Signals | TX_M, TX_P |
RX_M, RX_P | |
Clock Signal (6-Wire) | RXCLK_M, RXCLK_P |