10

ML4642

39

Ω

39

Ω

360

Ω

360

Ω

360

Ω

360

Ω

39

Ω

39

Ω

360

Ω

360

Ω

360

Ω

360

Ω

39

Ω

39

Ω

39

Ω

39

Ω

360

Ω

360

Ω

TXIN1P

TXIN1N

RXOUT1P

RXOUT1N

CDOUT1P

CDOUT1N

TXIN2P

TXIN2N

RXOUT2P

RXOUT2N

CDOUT2P

CDOUT2N

TXOUTP

TXOUTN

RXINP

RXINN

CDINP

CDINN

JAB1/JABD

JAB2

CDLED

TXLED1

TXLED2

RXLED/LPBK/SQE

GND

Switch Option

1. Receive LED with Internal/External MAU

2. No MAU/No SQE

3. No MAU with SQE

ML4642

0.1

0.01

+5V

61.9K

+5V

RRSET

510

Ω

510

Ω

510

Ω

510

Ω

270

Ω

270

Ω

2

+5V

3

TO MAU

TO DTE 1

TO DTE 2

1

Q1

1k

1k

7.15k

Q2

Before data will be transmitted to the TXOUT and RXOUT

pins from the TXIN pins it must meet the unsquelch

requirements of the TXIN receiver circuitry. The squelch

circuitry prevents any noise on the TXIN wires from being

misinterpreted as data and transmitted to the TXOUT and

RXOUT pins. The squelch circuit rejects signals with pulse

widths less than typically 20ns and voltage levels more

positive than –250mV. Once the TXIN receiver is

unsquelched it remains so until reception of the input idle

signal, which is detected when the TXIN signal is more

positive than –170mV for longer than 180ns.

RECEPTION

The receive function consists of detecting data at the

RXIN differential receiver of the MAU port transmitting

this data to both DTE port RXOUT pairs.

Figure 9 is a block diagram of a Two Port Multiplexer

using the ML4642 chip. All AUI interfaces are shown AC

coupled as they would be in an AUI multiplexer which

does not include the MAU circuitry on the same board.

TRANSMISSION

The transmit function consists of detecting data on either

of the TXIN differential receivers (TXIN1 or TXIN2) and

transmitting this data out the TXOUT differential driver at

the MAU port as well as both RXOUT1 and RXOUT2

drivers of the DTE ports. (Note: the looping back of data

received at a TXIN pair to the RXOUT pairs is discussed in

the Loopback section.)

Figure 9. Two Port AUI Multiplexer

FUNCTIONAL DESCRIPTION