ML4658
PIN DESCRIPTION (DIP) (Continued)
PIN# NAME
FUNCTION
12 POLRD
Receive Polarity status. Active low LED Driver, open collector output. Indicates the polarity of the
receive twisted pair regardless of auto polarity correction. When this pin is high, the receive polarity
is correct, and when this pin is low the receive polarity is reversed.
13 XMT
14 RCV
Indicates that transmission is taking place on the TxTP+, TxTP– pair. Active low LED driver, open
collector. It is extended 100ms for visibility.
Indicates that the transceiver has unsquelched and is receiving data from the twisted pair. Active low
LED driver, open collector. It is extended 100ms for visibility.
15 TxTP–
16 TxTP+
Pre-equalized differential balanced current driven output. These ouputs are connected to a balanced
transmit output filter which drives the twisted pair cable through pulse transformers. The output current
is set with an external resistor connected to RTSET allowing the chip to drive 100Ω unshielded twisted
pair, 150Ω shielded twisted pair cables or a range of other characteristic impedances.
17 GND
Ground reference.
18 TxCAP1
19 TxCAP0
An external capacitor of 330pF is tied between these two pins to set the pulse width for the pre-
equalization on the transmitter. If these two pins are shorted together, no pre-equalization occurs.
20 LTF
Link Test Fail. Active high. Normally this pin is low, indicating that the link is operational. If the link
goes down resulting from the absence of link pulses or frames being received, the chip will go into
the Link Test Fail state and bring LTF high. In the Link Test Fail state, both the transmitter and receiver
are disabled, however link pulses are still sent. A station that only has access to the AUI can detect a
Link Test Fail by the absence of loopback. This pin is low when the Link Test is disabled. Open
collector LED output.
21 RxTP–
Twisted Pair receive data input. When this signal exceeds the receive squelch requirements the
receive
22 RxTP+
23 BIAS
data is buffered and sent to the Rx± outputs.
Bias voltage, output. Used to bias the receive twisted pair inputs as well as the Tx± inputs when they
are AC coupled.
24 JAB
Open collector TTL output capable of driving an LED. When in the Jabber state, this pin will be low
and the transmitter will be disabled. In the Jabber “OK” state this pin will be high.
3
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