2. General Description
8308/8306 Preliminary Product Specification
Subject to change
The RTL8308/8306 provides eight/six 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 and link status can be
acquired by periodically polling the status of the PHY devices via MDIO.
2M ( or 32K x 64 ) bits, or 256K bytes DRAM operating in 50MHz clock is built-in as packet storage
buffer. To efficiently utilize the packet buffer, the RTL8308/8306 divides the 256K bytes DRAM into 1K
pages of storage spaces, i.e., per page contains 256 bytes. For Ethernet packets, the maximum of seven
pages are used and the minimum is one.
Address look-up table consists of two spaces. One is a 16K entries of hash table and another is a 128
entries of CAM. The RTL8308/8306 uses address hashing algorithm or direct mapping method to search
destination MAC address and record source MAC address from and to the hash table. If hashed or
mapped location is not empty, the RTL8308/8306 will compare the destination MAC address with the
contents of the CAM for address searching and store source MAC address to CAM for learning.
The RTL8308/8306 supports IEEE 802.3x full duplex flow control and half duplex back pressure
congestion control. The IEEE 802.3x flow control's ability is auto-negotiated between remote device and
the RTL8308/8306 by writing the flow control ability via MDIO to external connected PHY and restart
the auto-negotiation process. For half duplex, the RTL8308/8306 adopts a special back pressure design,
forwarding one packet successfully after 28 force collisions, to avoid the connected repeater being
partitioned due to lots of collisions. The full/half duplex flow control ability can be enable or disable via
The RTL8308 provides reversible PHYAD order feature to connect diverse external PHY devices via
EEPROM's setting. But 8306 doesn't support this function.
The RTL8308/8306 is capable to auto-detect the network loop (or bridge loop). When a loop is detected,
the loop LED is displayed. This capability can be enabled or disabled via ENLOOP pin.
The RTL8308/8306 supports non-blocking 148800 packets/second wire speed forwarding rate and special
design to resolve the head-of-line-blocking problem.
The RTL8308/8306 can enable broadcast storm control via ENBRDCTRL pin. Each port will drop
Datasheet pdf - http://www.DataSheet4U.net/