AX88850

PRELIMINARY

ASIX ELECTRONICS CORPORATION

21

3.6 Expansion Logic(Cascade Interface)

The expansion logic is used to stack numerous repeaters. The expansion logic can be divided into two types:

Expansion Logic with Buffer (maximum mode

In this mode, use /IR_ACTO[7:0] and /IR_ACTI[7:0] to cascade repeaters. Buffers are used both in

/IR_ACTO[7:0] and /IR_ACTI[7:0]. This mode is supposed to cascade repeaters on difference boards via cables.

There is a configuration bit /IR_ACT_EN to decide cascade signals are judges by /IR_ACTI[7:0](/IR_ACT_EN

= 0) or /IR_ACTO[7:0](/IR_ACT_EN = 1).

Expansion Logic without Buffer (minimum mode)

In this mode, use /IR_ACTO[7:0] to cascade repeaters. Just connect /IR_ACTO[7:0] without using buffer in this

part. This mode is supposed to cascade repeaters on the same board.

/IR_ACTO<7:0>

RPTR_ID<2:0>

Idle

Active

Collision

0

FFh

FEh

FBh

1

FFh

FDh

FCh

2

FFh

FBh

F9h

3

FFh

F7h

F3h

4

FFh

EFh

E7h

5

FFh

DFh

CFh

6

FFh

BFh

9Fh

7

FFh

7Fh

3Fh

In this table:

a.

All /IR_ACTO[7:0] will be in open-drain state when repeater chip is idle. These signals are all high via

external pull high resister.

b.

One signal of /IR_ACTO[7:0] is low in data forwarding state corresponding to different RPTR_ID[2:0].

c.

Two signals of /IR_ACTO[7:0] are low in collision state corresponding to different RPTR_ID[2:0].

3.7 Management Logic

AX88850 provides the required management information associated with a packet for management chip which

statistics processed on a per packet basis. Transmit ready signal TX_RDY is used as a framing signal for management

data MD. Then management chip uses this data to determine the source of the current packet. MD data is synchronized

to the rising edge of IRD_CK. When collision occur, MD will be tri-state and becomes invalid.

MD frame format

idle

start bit

data0

data1

data2

data3

data4

data5

data6

1

0

PID[0]

PID[1]

PID[2]

PID[3]

PID[4]

RID_CH

PARITY

Notes:

a.

PID[4:0] is the number of the receiving port.

b.

RID_CH indicates change in RID.

c.

PARITY = 1 when sum of 1‘s among PID[4:0] and RID_CH is even

PARITY = xnor (PID[4],PID[3],PID[2],PID[1],PID[0],RID_CH)