ASIX ELECTRONICS CORPORATION

12

CONFIDENTIAL

AX88873P 10/100Mb Repeater Controller PRELIMINARY

3.0 Functional Description

3.1 Repeater State Machine

The repeater state machine is in idle state when there is no carrier presented on any ports . When there is only

one port has receive activity, the repeater state machine will enter data -forwarding state to ensure correct

data forwarding to other connected ports. If collision happens anytime, The repeater state machine detects

collision then send jam pattern to all ports until collision ceases.

3.2 RXE /TXE Control

Idle state

CRS_DV(ALL) = 0, the repeater sends no data to any port.

RXE(ALL) = 0.

TXE(ALL) = 0.

Data Forwarding state

If CRS_DV(ALL) = 1, N is the only one port that has incoming packet.

RXE(N) = 1, RXE(ALLXN) = 0.

TXE(N) = 0, TXE(ALLXN) = 1.

Collision state

If CRS_DV(ALL) > 1, the repeater sends jam pattern to all ports.

RXE(ALL) = 0.

TXE(ALL) = 1.

One Port Left state

When all packets are back off except only one port still has activity, that is CRS_DV(ALL) = 1 again . N is the

only one left port that has incoming packet. The repeater sends jam pattern to all other port except for the still

activity ports.

RXE(ALL) = 0.

TXE(ALLXN) = 1.

3.3 Jabber State Machine

To prevent an illegally long reception of data from reaching the repeater unit, each port has its own jabber

timer. If a reception exceeds this duration (64K bit times for AX88872A), the jabber condition will be detected.

In this condition, repeater unit will disable receive and transmit packets for the jabbered port and the other ports

remain the normal operation.

When the carrier is no longer detected for the jabbered port or reset the repeater, the jabber state will be existed

and the port will receive and transmit packets normally.

3.4 Partition State Machine

The partition state machine is used to protect network from being upset when a port suffer continuous

collision, each port uses a partition state machine to detect and prevent this condition. When a port suffers from

continuous 64 times of collision events, then it goes to Partition State. The partitioned port will be not released

until a packet without collision be transmitted( more than 512 bit times for AX88872A) or reset the repeater.