CS8904-CM5 データシートの表示（PDF） - Cirrus Logic

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CS8904-CM5

Crystal LAN™ Quad Ethernet Transceiver

Cirrus Logic 

CS8904

Crystal LAN™ Quad Ethernet Transceiver

CS8904 will keep the transmitter disabled until

TxENBL has been deasserted and TxDATA has

been idle for at least 420 ms.

4.3.1.3 Collision Indication

When operating half duplex, the reception of data

from the network during the normal transmission

of data indicates a collision has occurred. If this

condition is detected, the CS8904 will cause the

COLL pin to be raised. Following that, when the

CS8904 detects a transition on the TxENBL pin or

the termination of the data received on the Rx+/Rx-

pins, then the CS8904 will cause the COLL pin to

deassert. Normally, the COLL signal is used by the

controller to, among other things, initiate a jam

sequence. (An arbitrary set of bits of sufficient

number to assure that all communicating stations

detect a collision.)

Note that, by definition, collisions cannot occur

when operating full duplex.

4.3.1.4 Normal Reception

Received data is provided to the controller on the

RxDATA pin. The data is synchronized by the

clock recovered from the Manchester encoded data

received from the 10BASE-T Ethernet network.

The receive clock is output on the RxCLK pin. The

CS8904 indicates the beginning and ending of the

reception of valid data by causing a transition of the

CD pin.

4.3.2 Control and Status Information

Control and status signals are provided to select

and monitor the operational characteristics of each

port.

4.3.2.1 Auto-Negotiation and Duplex Selection

Auto-Negotiation allows the CS8904 to

communicate with the remote Ethernet device to

select the highest common duplex capability that

the two devices share. The CS8904 is fully

compliant with the relevant portions of section 28

of the Ethernet standard (ISO/IEC 8802-

3:1995(u)). Auto-Negotiation may be configured

differently for each individual port of the CS8904.

Setting the AUTOSEL pin high indicates that the

port will attempt to Auto-Negotiate duplex

selection with the remote end of the link. The

capability that will be advertised for this port is

determined by the DUPSEL pin. Setting the

DUPSEL pin high indicates that half or full duplex

capability may be negotiated. Setting the DUPSEL

pin low indicates that only half duplex capability

may be negotiated.

Setting the AUTOSEL pin low indicates that Auto-

Negotiation on the port is disabled. The DUPSEL

pin then determines the duplex operation of the

port. If the DUPSEL pin is set high, then the port

will only operate full duplex, otherwise if the

DUPSEL is set low, then the port will only operate

half duplex.

In either case, the outcome of duplex selection is

available for the controller on the DUPLEX and

AUTONEG pins. The DUPLEX pin indicates that

the port is operating half duplex if the output is low

and indicates that the port is operating full duplex

if the output is high. The AUTONEG pin indicates

whether the duplex selection occurred as a result of

a successful negotiation, as a result of explicit

selection using the DUPSEL pin, or as the result of

a failed attempt to Auto-Negotiate. Table 3

illustrates the possible outputs of the AUTONEG

and DUPLEX pins and their respective meanings.

CIRRUS LOGIC ADVANCED PRODUCT DATABOOK

DS191PP2

17

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