DP83916 datasheet(45/96 Pages) NSC

45 / 96 page

50 Bus Interface (Continued)

52 PIN DESCRIPTION

input

output and

TRI-STATE Inputs are TTL compatible

ECL e ECL-like drivers for interfacing to the AUI interface

Totem pole like drivers These drivers are driven ei-

ther high or low and are always driven Drive levels

are CMOS compatible

TRI e TRI-STATE drivers These pins are driven high low

or TRI-STATE Drive levels are CMOS compatible

These pins may also be inputs (depending on the

pin)

OC e Open Collector type drivers

These drivers are

TRI-STATE when inactive and are driven low when

active These pins may also be inputs (depending

on the pin)

TABLE 5-1 Pin Description

Symbol

Driver

Direction

Description

Type

NETWORK INTERFACE PINS

EXT

External ENDEC Select

Tying this pin to VCC (EXT e 1) disables the internal ENDEC

and allows an external ENDEC to be used Tying this pin to ground (EXTe0) enables

the internal ENDEC This pin must be tied either to VCC or ground Note the alternate

pin definitions for CRSoCRSi COLoCOLi RXDoRXDi RXCoRXCi and TXCoTXCi

When EXTe0 the first pin definition is used and when EXTe1 the second pin definition

is used

CDa

Collision a

The positive differential collision input from the transceiver This pin should

be unconnected when an external ENDEC is selected (EXT e 1)

CDb

Collision b

The negative differential collision input from the transceiver This pin

should be unconnected when an external ENDEC is selected (EXT e 1)

RXa

Receive a

The positive differential receive data input from the transceiver This pin

should be unconnected when an external ENDEC is selected (EXT e 1)

RXb

Receive b

The negative differential receive data input from the transceiver This pin

should be unconnected when an external ENDEC is selected (EXT e 1)

TXa

ECL

Transmit a

The positive differential transmit output to the transceiver This pin should

be unconnected when an external ENDEC is selected (EXT e 1)

TXb

ECL

Transmit b

The negative differential transmit output to the transceiver This pin should

be unconnected when an external ENDEC is selected (EXT e 1)

CRSo

Carrier Sense Output (CRSo)

from the internal ENDEC (EXT e 0) When EXT e 0 the

CRSo signal is internally connected between the ENDEC and MAC units It is asserted

CRSi

on the first valid high-to-low transition in the receive data (RXa b) This signal remains

active 15 bit times after the last bit of data Although this signal is used internally by the

SONIC-16 it is also provided as an output to the user

Carrier Sense Input (CRSi)

from an external ENDEC (EXT e 1) The CRSi signal is

activated high when the external ENDEC detects valid data at its receive inputs

COLo

Collision Output (COLo)

from the internal ENDEC (EXT e 0) When EXT e 0 the

COLo signal is internally connected between the ENDEC and MAC units This signal

COLi

generates an active high signal when the 10 MHz collision signal from the transceiver is

detected Although this signal is used internally by the SONIC-16 it is also provided as

an output to the user

Collision Detect Input (COLi)

from an external ENDEC (EXT e 1) The COLi signal is

activated from an external ENDEC when a collision is detected This pin is monitored

during transmissions from the beginning of the Start Of Frame Delimiter (SFD) to the

end of the packet At the end of transmission this signal is monitored by the SONIC-16

for CD heartbeat

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