W89C92 Ver la hoja de datos (PDF) - Winbond

Número de pieza

componentes Descripción

Lista de partido

W89C92

TRANSCEIVER FOR COAXIAL CABLE (TCC)

Winbond 

W89C92

Timing Waveforms, continued

Test Conditions

Input Signal with 30 nS

Rise and Fall Times

R = 1K

C = 36 pF

RXI

W89C92

Receiver

DO+/-

Output

R and C network

simulates worst case

cable jitter

APPENDIX

External MAU Implementation

An external MAU can be implemented using the W89C92 and a 9V DC power supply, which may be a

DC-to-DC converter. A 12V to 9V DC-to-DC converter is recommended for recovering the voltage

drop through the 50-meter AUI twisted pair cable. A 0.1 µF decoupling capacitor connected between

the 9V output and ground of the converter is recommended.

The isolation requirement between DTE and MAU can be met using a one-to-one ratio pulse

transformer or a set of coupling capacitors. Recommended transformers are Pulse Engineering

#64103, Valor Electronics #1101, or an equivalent, and the recommended capacitor is 0.1 µF/1 KV.

The pull-down resistor for the differential output pair (CSO+/-, DI+/-) should be 500 ohms to drive the

78 ohm AUI twisted pair line with sufficient voltage swings. A 78 ohm resistor should be shunted

between the differential receive pair (DO+/-) to match the impedance of the AUI cable. To establish

the proper operating point of the W89C92, a precision 1K 1% ohm resistor should be connected

between ER+ and ER-.

A voltage divider is used to program the SQE test function and the jabber lockup function. The SQE

test function can be disabled by connecting SQE to VSS. The jabber lockup function is disabled when

the SQE is set to between -3.4V and -5.4V. The CLS of the W89C92 should be connected to VDD to

allow the W89C92 to detect collision conditions in transmit mode. Other settings on CLS will not

guarantee that the W89C92 will detect collisions correctly.

A diode should be used to isolate the capacitance loading from the cable. The input capacitance of

the 1N4148 diode is 2pF, which meets the input impedance required for the IEEE 802.3 10BASE5

MAU function. A 1M shunt resistor and a 0.01 µF/1 KV shunt capacitor between the coaxial cable

ground and DTE ground will provide the DC and AC discharge path for the external MAU.

Internal MAU Implementation

An internal MAU is embedded in the DTE, so the AUI cable and 78 termination resistor are not

needed. A 5V to 9V DC-to-DC converter can be used as the power supply instead of the 12V to 9V

converter.

Publication Release Date: September 1994

-9-

Revision A3

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