AX88871AP Bripeater

ASIX ELECTRONICS CORPORATION

17

The repeater sends jam pattern to all other port except for the still activity port.

RXE(ALL) = 0, RXE_IR = 0.

TXE(ALL-X) = 1, TXE_IR = 0. Suppose X is the one left port.

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 AX88871A), 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 function will be

clear and re-enable reception and transmission.

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 suffer 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 AX88871A) or reset the repeater.

3.5 Expansion Logic(Cascade Interface)

The expansion logic is used to stack numerous repeaters to expend the number of connected ports. The

expansion logic can be divided into two types:

Expansion Logic without Buffer (minimum mode)

In this mode, use /IR_ACTO[7:0] to cascade repeaters in back plane. Just connect /IR_ACTO[7:0] of

all repeaters without using buffer. This mode is supposed to cascade repeaters on the same board. In this

application, the stackable system can reach to 4 repeaters.

Expansion Logic with Buffer (maximum mode)

This mode is entered with the setting of /DIS_DMII = 0, the dedicated port isn‘t existed again in this

mode. Now the dedicated pins DRXD[3:0], DCRS, DRX_DV, DRX_ER, DRX_CLK play a role as

IR_ACTI[7:0]. Use /IR_ACTO[7:0] and /IR_ACTI[7:0] to cascade repeaters in back plane. Buffers

are used both in /IR_ACTO[7:0] and /IR_ACTI[7:0]. The mode is supposed to cascade repeaters on

different boards via cables. In this application, the stackable system can reach to 8 repeaters.

/IR_ACTO<7:0> are driven according to repeater ID and receive activity of local connected ports as

follows:

Repeater ID

IDLE state

Only One Port Activity

More than One Port Activity

000

11111111

11111110

11111100

001

11111111

11111101

11111100

010

11111111

11111011

11111001

011

11111111

11110111

11110011

100

11111111

11101111

11100111

101

11111111

11011111

11001111

110

11111111

10111111

10011111

111

11111111

01111111

00111111

Note: All /IR_ACTO[7:0] will be in open-drain status when they aren‘t driven. These signals present high

via external pull high resister.

3.6 Data Flow control