參數(shù)資料
型號: EM2H
廠商: LSI CORP
元件分類: 網(wǎng)絡(luò)接口
英文描述: 10Base-2 Ethernet Transceiver Module with On Board Isolation Transformer & DC/DC Converter(10Base-2 以太網(wǎng)收發(fā)器模塊(帶絕緣變壓器和 DC/DC變換器))
中文描述: DATACOM, ETHERNET TRANSCEIVER, DIP14
文件頁數(shù): 4/12頁
文件大?。?/td> 124K
代理商: EM2H
Ether Module - EM2H
10Base-2
MD400153/B
4
A 4-pole Bessel low-pass filter provides the average DC
level from the received signal. It sends this level to the
Collision Comparator and RX Squelch circuits. The
squelch circuit activates he Receive Line Driver only when
it detects a true signal. This prevents noise triggering the
receiver.
When a packet s detected, he DC evel rom he Low-pass
Filter becomes more negative han he DC squelch hresh-
old, and the Receiver turns on. The squelch circuit AC
timing detects high level signals of more than 225 nanos-
econds, and urns he Receiver off. If within 1 microsecond
(typical) the low_pass filter level becomes more positive
than the DC squelch threshold, then the receiver stays off.
See the Receiver Timing Diagram, Figure 4.
The System Connections diagram shows the transceiver
connections in a station environment. RX
±
and CD
±
differential signals to the MCC are biased by 1.0 K ohm
pull-down resistors and are isolated from the MCC. The
DC supply is converted to –9V by a DC to DC converter.
This converter also provides DC isolation between the +5
volt and –9 volt sides.
The COAX center conductor connects to the Receive and
Transmit pins of the transceiver. An internal diode
minimizes network oading when power s on or off. COAX
tap capacitance contributed by the Thin Net module s ess
microsecond starting about 1.1 microseconds after the
end of transmission. This test can be disabled for opera-
tion with repeaters by connecting the HBE pin to V
EE
.
The Jabber Timer
The Jabber Timer monitors the operation of the Transmit-
ter, using the 10 MHz Oscillator as a time base. If the
Transmitter operates continuously for more than typically
40 Milliseconds, the Jabber Timer disables the Transmit-
ter and enables the Collision Detector outputs. The
Transmitter is automatically re-enabled after the station
has been silent for 500 milliseconds.
The Receiver
The Receiver detects any signal on the COAX center
conductor that triggers its squelch circuits, and sends the
signal through a differential line driver to the MCC. The
Receiver provides amplification and equalization; a
squelch circuit prevents noise rom activating he Receiver
circuits. See Figure 4.
The receive signal goes through a buffer with a high input
impedance and low capacitance to reduce loading and
reflections on the network COAX. An equalizer passes
high frequencies and attenuates low frequency signals
from the network, flattening the network pass band. The
signal s output through a differential ine driver presenting
a balanced signal to the station. The line driver has 4
nanosecond rise and fall times.
Figure 4. Receiver Timing
RX±
RXI
tRON
50%
tRd
90%
50%
tRf
RECEIVER
SQUELCH
LOW-PASS
FILTER
RECEIVE
ENABLE
DC
THRESHOLD
DC
THRESHOLD
1 μs
t
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