Realtek PDF datasheets for RTL8308

The RTL8308B is a 128-pin, low cost and ultra low power consumption 8-port 10/100M Ethernet switch controller. It is integrated both with a 2M bit embedded DRAM, as a packet buffer, and an 8K entry address table. The RTL8308B supports the reduced MII (RMII) interface. Only a single 50MHz oscillator is needed and the EEPROM is optional, which can save BOM costs. In addition, the RTL8308B provides an LED display to indicate a network loop existence.

The RTL8308B provides eight 10/100 Mbps RMII Ethernet ports. Each port can operate in 10 Mbps or 100 Mbps data rate, and in full or half duplex mode. Speed, duplex, link status and flow control can be acquired by periodically polling the status of the PHY devices via MDIO.

The address look-up table consists of an 8K entry hash table and a 128 entry CAM. The RTL8308B uses the address hashing algorithm or direct mapping method to search destination MAC addresses from and record source MAC addresses to the hash table. Data received from the MAC interface is stored in the external memory buffer.

The RTL8308B supports IEEE 802.3x full duplex flow control and half duplex back pressure control. The ability of IEEE 802.3x flow control is auto-negotiated by writing the flow control ability via MDIO. The reversible PHYAD order feature is provided to connect diverse external PHY devices for PCB layout.

The RTL8308B provides a loop detect LED for visual diagnostics when detecting the network loop. The Broadcast storm filtering function is provided for unusual broadcast storm traffic.

The RTL8308B supports non-blocking 148800 packets/second wire speed forwarding rate and a special design to resolve the head-of-line-blocking problem. The RTL8308B uses a 2-wire 24LC02 interface to access the external serial EEPROM, which is not required. Only one 50MHz OSC is needed.