NE83Q93 查看數據表（PDF） - Philips Electronics
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NE83Q93 Datasheet PDF : 11 Pages
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Philips Semiconductors
Enhanced coaxial Ethernet transceiver
Product specification
NE83Q93
Control Interface Signals
The NE83Q93 provides two input and one output signal for mode
control and interfacing within repeaters. The output signal is Carrier
Sense (CRS) and the input signals are Heartbeat Enable (HBE) and
Transmit Enable (TEN).
The HBE input controls the transmission of the heartbeat (or SQE)
signal to the DTE for testing the collision detection function. It is
normally hardwired to VEE or GND.
1. The heartbeat (SQE) function is DISABLED when HBE is
connected to VEE
2. The heartbeat (SQE) function is ENABLED when HBE is
connected to GND or left floating
The TEN input controls the coaxial transmitter. It is a CMOS
compatible input requiring a driving signal with a voltage range of
VEE to VEE + 5V. It is normally driven through an opto-coupler to
provide electrical isolation. A typical application circuit is shown in
Figure 2.
1. The coaxial transmitter is DISABLED when a LOW is applied to
TEN or it is directly connected to VEE. Since the loopback
function of the NE83Q93 occurs through the coaxial connection
the loopback function is also disabled.
2. The coaxial transmitter is ENABLED when a HIGH is applied to
TEN or it is directly connected to GND or left floating.
The CRS output indicates the presence of a carrier signal on the
coaxial cable. It is open drain output designed to drive the LED of
an opto-coupler connected between CRS and LCOM through a
current limiting series resistor. A LOW at CRS is VEE and a HIGH is
the voltage at LCOM (VEE + 5V).
1. CRS is HIGH (no current) when no carrier is present
2. CRS is LOW (current sinking) when carrier is present
On applying a HIGH to TEN through an opto-coupler the transmitter
is enabled but it still has to recognize the normal squelch-qualified
01 bit sequence with the negative-going differential signals meeting
the necessary magnitude and duration requirements. The set-up
time needed from application of a HIGH at TEN to recognizing the
first 01 bit sequence is typically 25ns. The propagation delay
through an opto-coupler is of the order of 200ns.
AUI Selection/Under Voltage Lockout
The transmit and receive squelch circuits of the NE83Q93 remain
active if the absolute value of VEE is less than the threshold for
under voltage lockout, VUVL. This prevents glitches from appearing
on either the AUI or coaxial cable during power up and power down.
There is no collision announcement during power up and the
transceiver waits for 400ms before becoming enabled.
If RXI is disconnected from the coaxial cable after power up, its
voltage will fall towards VEE. If the absolute value of this voltage
exceeds the AUI disable voltage, VDIS, for longer than 800ms, the
transmit and receive squelch circuits remain active and, in addition,
the AUI drivers become high impedance. This permits AUI
connections to be hard wired together, e.g., the coaxial transceiver
and a 10BASE-T transceiver, with the signal path determined by
which transceiver is connected to its external cable.
There is a 400ms collision announcement on disconnecting RXI, but
there is no announcement on re-connection. This feature can be
disabled by pulling RXI up with a 200kΩ to ground.
Detection of Coaxial Cable Faults
In the NE83Q93 there is no internal loopback path from the TX
inputs to the RX outputs. This means that, when the local DTE is
transmitting, the signal will only be present at the receiver outputs
RX+ and RX– if it appears on the coaxial cable and is larger than
the receiver squelch threshold VRS. If a short circuit fault condition
occurs at the cable connector to the CTI, then no signal will appear
at the receiver outputs.
In the case of an open circuit at the coaxial cable connector there
will also be no signal at the receiver outputs due to the AUI disabling
mode of the NE83Q93. However, a heartbeat signal will be present
following a transmission attempt for the short circuit condition, but
not for the open circuit.
A coaxial cable with only a single 50Ω termination will generate a
collision not only at every transmission attempt, but also for every
reception attempt due to the receive mode collision detection of the
NE83Q93.
Status Indicator Functions
The NE83Q93 provides five status outputs, the open drain device
connected to each is capable of directly driving an LED or
opto-coupler, or other logic circuits if an external pull-up resistor is
used. The functional descriptions below are for an LED connected
between the output and LCOM (VEE + 5V) through a current limiting
series resistor.
The LINK signal indicates the status of the coaxial connection.
• The LED is ON when the transceiver is connected to a properly
terminated coaxial cable.
• The LED is OFF when the coaxial cable is disconnected from the
transceiver, or if the coaxial connection is unterminated.
The XLED signal indicates the status of the transmitter.
• The LED is OFF when there is no transmission in progress
• The LED is turned ON when data is being transmitted and
remains ON for typically 115ms.
The RLED signal indicates the status of the receiver.
• The LED is OFF when no signal is being received.
• The LED is turned ON when data is received and remains ON for
typically 115ms.
The CLED signal indicates the status of the collision detection
circuit.
• The LED is OFF for no collision.
• The LED turns ON when a collision is detected and remains ON
for typically 12ms after the end of the collision.
• In the event of another collision during the latter 6ms of the 12 ms
delay period after the end of the last collision, the LED will turn off
for typically 6ms then back ON to indicate the new collision.
The JLED signal indicates the status of the jabber control circuit.
• The LED is OFF for a no-jab condition.
• The LED turns ON when the coaxial transmitter output is jabbed.
• The LED turns back off when the transmitter is unjabbed.
1995 May 1
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