ASIX ELECTRONICS CORPORATION

4

CONFIDENTIAL

AX88872P Swipeater Controller

PRELIMINARY

1.0 AX88872 Overview

1.1 General Description

The AX88872 that built in a switch is not only a simple repeater but also it provide 2 repeater expansion buses for

10M and 100M respectively. So the cascade function of the AX88872 can be backward compatible with the AX88871A

“Bripeater” in virtual switch mode. Also the AX88872 can support Master/Slave mode in stack application. That all the

repeater stack system forms one 100Mbps segment and one 10Mbps segment in Master/Slave mode. The two segments

are communication via the switch of the master chip.

In general, using RMII interface for 8 repeater ports can simplify the design and also provide a low cost solution with

RMII Quad/Octet PHY and low cost 64Kx32 SSRAM as buffer memory. In additional, the AX88872 provides two

10/100M MII/RMII switch ports alternative for up-link and down-link function. AX88872 has counterpart AX88873

that is a simple dual-speed repeater controller without built-in switch.

The switch port3 is fixed to 10Mbps speed and connect to 10Mbps repeater segment, The switch port2 is fixed to

100Mbps and connect to 100M repeater segment. The other switch ports 0 and 1 are connected to external MII or RMII

interfaces for various applications.

The built-in switch provides 4/8K look-up table that can learn, route and age with MAC address of each packet

automatically for packet forwarding and filtering. That is, the AX88872 forwards and filters packets with DA

(Destination Address) and the table. The performances of routing and learning fit wire speed (148800 packets/sec at

100Mbps). The switch provides three packet forwarding mode: Store-and-Forward, Fragment-Free (i.e., safe cut-

through) and auto mode. Dynamically the switch selects optimum mode for packet forwarding based on network quality.

During transmission, the data is obtained from the buffer memory and routed to the destination port. For half-duplex

operation, when collision occurs, the MAC controller will back off and retransmit in accordance to the IEEE802.3

specification. The switch also support flow-control mechanism. For full duplex operation mode, 802.3x flow control is

supported. For half-duplex operation, an optional jamming based flow control is available to avoid loss of data. This is

also well known as back-pressure. The flow control function is optional.