ML4642
FUNCTIONAL DESCRIPTION
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
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.)
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.
+5V
V
V
CC
TXIN1P
TXIN1N
CC
0.01
0.1
GND
39Ω
39Ω
+5V
RRSET
ML4642
61.9K
RXOUT1P
TXOUTP
TXOUTN
TO DTE 1
RXOUT1N
360Ω
360Ω
39Ω
360Ω
360Ω
39Ω
360Ω
360Ω
CDOUT1P
CDOUT1N
RXINP
RXINN
TO MAU
39Ω
39Ω
39Ω
39Ω
TXIN2P
TXIN2N
CDINP
CDINN
RXOUT2P
RXOUT2N
TO DTE 2
JAB1/JABD
JAB2
270Ω
360Ω
360Ω
360Ω
360Ω
510Ω
510Ω
510Ω
510Ω
CDLED
CDOUT2P
CDOUT2N
TXLED1
TXLED2
1
2
3
RXLED/LPBK/SQE
270Ω
7.15k
+5V
Switch Option
1. Receive LED with Internal/External MAU
2. No MAU/No SQE
3. No MAU with SQE
Q1
1k
Q2
1k
Figure 9. Two Port AUI Multiplexer
10
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
