- DISTINCTIVE CHARACTERISTICS
- BLOCK DIAGRAM
- RELATED PRODUCTS
- CONNECTION DIAGRAMS
- ORDERING INFORMATION
- PIN DESCRIPTION
- FUNCTIONAL DESCRIPTION
- LAYOUT CONSIDERATIONS
- ABSOLUTE MAXIMUM RATINGS
- OPERATING RANGES
- DC CHARACTERISTICS
- SWITCHING CHARACTERISTICS
- KEY TO SWITCHING WAVEFORMS
- SWITCHING TEST CIRCUIT
- SWITCHING WAVEFORMS
Issue Date: May 1994
IEEE 802.3 10BASE-5 and10BASE-2
is transmitted onto the network
other networking applications
ceiver suppor ts Ethernet Version 2, IEEE 802.3
10BASE-5 and IEEE 802.3 10BASE-2--Cheapernet)
transceiver applications. Transmit, receive, and colli-
sion detect functions at the coaxial media interface to
the data terminal equipment (DTE) are all performed by
this single device.
Am7996 interfaces the coaxial (0.4
10BASE-2--Cheapernet applications, the Am7996 typi-
cally resides inside the DTE with its signals to the DTE iso-
lated and the coaxial (0.2
both applications are isolated from that of the DTE.
current drive for data signaling onto the media. The jabber
controller prevents the node from transmitting exces-
sively. While transmitting, collisions on the media are de-
tected if one or more additional stations are transmitting.
that provides a signal on the Cl pair at the end of every
transmission. The SQE Test indicates the operational
status of the Cl pair to the DTE. It can also serve as an
acknowledgment to the node that packet transmission
onto the coax was completed.
Pin 1 is marked for orientation.
NC = No Connection
by a combination of the elements below.
ported in volume for this device. Consult the local AMD sales
office to confirm availability of specific valid combinations and
to check on newly released combinations.
IEEE 802.3/Ethernet/Cheapernet Transceiver
Blank = Standard Processing
B = Burn-In
TR = Tape and Reel Packaging
C = Commercial (0
P = 20-Pin Plastic DIP (PD 020)
D = 20-Pin Ceramic DIP (CD 020)
J = 20-Pin Plastic Leaded Chip Carrier (PL 020)
requirements and carrier sense levels are outputted at
tected at DO
oscillator signal to the AUI interface. For proper compo-
nent values at COLL OSC, signaling at Cl
squelch detect receiver with offset and noise filtering
and a data receiver with zero offset for data signal pro-
cessing. Signals meeting squelch requirements are
waveshaped and output at TXT.
nals and direct coupling for Carrier Detect and SQE av-
erage level detection. Signals at RXT meeting carrier
squelch enable data to the Dl
COLL OSC frequency to Cl
plifier. This l/O port is to be connected to the media
through an isolation network and a low-pass filter. Sig-
nals meeting DO
time current pulse. When operated into a double termi-
pulse-width distortion, rise and fall times, and harmonic
content. The sense amplifier monitors TXT faults and
and SQE output drive levels are set. SQE frequency
set is also determined by components connected be-
SQE TEST pin to V
dundant jabber. Transmit level is set by an external re-
sistor between V
a positive power supply.
An internally set analog reference for SQE level and data
signal set at 1.600 V nominal with a source resistance
justing threshold levels for other applications).
ceiver consists of four sections: 1) Transmit--receives
signals from DTE and sends it to the coaxial medium;
2) Receive--obtains data from media and sends it to
DTE; 3) Collision Detect--indicates to DTE any colli-
sion on the media; and 4) Jabber--guards medium
from node transmissions that are excessive in length.
(in the case of Am7990 family applications, from the
Am7992 --serial interface adapter--SIA). For IEEE
(10BASE-5)/Ethernet applications, this signal is re-
ceived through the AUI cable and isolation transformer.
In IEEE 802.3 10BASE-2--Cheapernet applications,
the AUI cable is optional.
jects signals with pulse widths less than 7 ns (negative
going), or with levels less than 175 mV peak. Only sig-
nals greater than 275 mV peak from the DTE are en-
abled. This minimizes false starts due to noise and
ensures that no valid packets are missed.
to ensure adequate signal level at the end of the maxi-
mum length network segment (500 meters) under the
worst-case number of connections (100 nodes). Re-
quired rise and fall times of data transmitted on the net-
work are maintained by the Am7996 Tap Driver. The tap
driver's output is connected to the media through exter-
nal isolating diodes. To safeguard network integrity, the
driver is disabled whenever power falls below the mini-
mum operation voltage.
monitors the duration that the transmit tap driver is ac-
tive and disables the driver if the jabber time is ex-
ceeded. This prevents network tie-up due to a
"babbling" transceiver. Once disabled, the driver is not
reset until 400 ms after the DO pair is idle and there is
no fault on TXT. During the disable time, an SQE signal
is sent on the Cl pair to the DTE.
signal is a self-test indication to the DTE that the media
attachment unit (MAU) collision pair is operational.
impedance (100 k
noise) DC-coupled input amplifier in the Am7996 re-
ceives the signal. The received signal passes through
a high-pass filter to minimize inter-symbol distortion,
and then through a data slicer. The Am7996 Carrier
Detect compares received signals to a reference.
Signals meeting carrier squelch requirements enable
from the start of the packet.
an isolation transformer to the AUI cable (Ethernet/
lEEE 802.3--10BASE-5). In IEEE 802.3 10BASE-2--
Cheapernet, the AUI cable is optional. Following the
last transition of the packet, the Dl pair is held HIGH for
two bit times and then decreases to idle level within
twenty bit times.
more additional stations are transmitting on the network.
threshold reference. If the level is more negative than
the reference, an enable signal is generated to the Cl
pair. The collision threshold can be modified by
the differential Cl pair to the DTE through an isolation
collision, the SQE Test is in progress, or the jabber con-
troller is activated. The oscillator is also utilized in
counting time for the jabber timer and SQE Test.
at the end of the packet, decreasing to the idle level
within twenty bit times.
DO pair and senses TXT faults. It inhibits transmission
if the tap driver is active for longer than the jabber time
(26 ms). An SQE message (10 MHz collision signal), is
enabled on the Cl pair for the fault duration.
unjab time of 400 ms before it enables the driver.
mented externally, and the output driver disabled by re-
moving the driver supply at V
pair during the disable time.
if the SQE TEST pin is tied to V
sures that the twisted-pair assigned for collision notifica-
tion to the DTE is intact and operational. The SQE Test
starts eight bit times after the last transition of the trans-
mitted signal and lasts for a duration of eight bit times.
SQE TEST pin to V