CS8900 데이터 시트보기 (PDF) - Cirrus Logic

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CS8900

Highly-Integrated ISA Ethernet Controller

Cirrus Logic 

5.8 Full duplex Considerations

The driver should not bid to transmit a long

frame (i.e., a frame greater than 118 bytes) if the

prior transmit frame is still being transmitted.

The end of the transmission of this prior frame is

indicated by a TxOK bit being set in the

TxEvent register (register 8).

5.9 Auto-Negotiation Considerations

When the CS8900 is connected to an auto nego-

tiation hub, and if auto-media detection is

selected (bits 8 and 9 of register 13), then the

CS8900 may not auto-select the 10BASE-T me-

dia. The cause of this situation is described in

the following paragraphs.

The original IEEE 802.3 specification requires

the MAC to wait until 4 valid link-pulses are re-

ceived before asserting Link-OK. Any time an

invalid link-pulse is received, the count is restart-

ed. When auto-negotiation occurs, a transmitter

sends FLPs (auto-negotiation Fast Link Pulses)

bursts instead of the original IEEE 802.3 NLP

(Normal Link Pulses).

If the hub is attempting to auto-negotiate with

the CS8900, the CS8900 will never get more

than 1 "valid" link pulse (valid NLP). This is not

a problem if the CS8900 is already sending link-

pulses, because when the hub receives NLPs

from the CS8900, the hub is required to stop

sending FLPs and start sending NLPs. The NLP

transmitted by the hub will put the CS8900 into

Link-OK.

However, if the CS8900 is in Auto-Switch mode,

the CS8900 will never send any link-pulses, and

the hub will never change from sending FLPs to

sending NLPs.

106

CS8900

DS150PP2

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