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Ether Module - EM2C Ether Module TM-EM2C 10Base-2 10Base-2
Ethernet Transceiver Module with on Board Isolation Transformer & DC/DC Converter
97176
Introduction
The Thin Net (Cheapernet) module provides a complete Local Area Network interface for a station, without a transceiver cable. The EM2C is an encased module containing all circuit components for a complete Thin Net COAX interface and includes an on-board SEEQ CMOS 83C92C transceiver DC/DC converter and isolation transformer. The module is compatible with ANSI/IEEE 802.3 and ISO 8802-3. The module is part of a chipset manufactured by SEEQ Technology to provide the basic components for a LAN interface board. The other components include the 80C03, 8005/80C04A Advanced Ethernet Data Link Controllers (AEDLC TM), the 8020 or 8023A Manchester Code Converter (MCC TM), and the 80C24 Media Interface adapter (MIA).
Note: Check for latest Data Sheet revision before starting any designs. SEEQ Data Sheets are now on the Web, at www.lsilogic.com. This document is an LSI Logic document. Any reference to SEEQ Technology should be considered LSI Logic.
s Regulated DC to DC Converter on board. s Collision Test Generator, externally deselectable to work with any ANSI/IEEE 802.3 and ISO 8802-3 repeater. s Detects and reports network collisions in both transmit and receive modes. s Implemented with SEEQ proprietary high voltage (20V) and high performance CMOS process. s Loopback test detects network cable opens or shorts. s Power On Reset prevents transmission during power up. s Disable pin to power-down module. s Isolation Transformer on board. s Optimized for Hub and Repeater Applications. s EM2C is Available for Adapter Card Applications
Features
s The module is compatible with ANSI/IEEE 802.3 and ISO 8802-3 Standards for Thin Net (10BASE2). s Contains all Thin Net COAX transceiver functions within a single encased unit. s Squelch circuits on all signal inputs to eliminate noise.
RX + RECEIVE TO STATION RX -
3
LINE DRIVER 1.0 K 1:1 1.0 K VEE 1.0 K VEE _ 18 LOW PASS FILTER - + COLLISION TEST GENERATOR 10 MHz OSILLATOR JABBER TIMER COLLISION COMPARATOR + V EE RX SQUELCH COAX CABLE
4
CD + COLLISION SIGNAL TO STATION CD - V EE VCC SYS GND DM
1
1:1
2 LINE DRIVER 11 10 9 12 TX SQUELCH TX + 5 V EE REGULATED DC/DC CONV GND 1.0 K
TRANSMIT FROM STATION TX -
6 1:1
TRANSMITTER
Figure 1. Ethernet Transceiver Module Block Diagram
AEDLC, MCC and Ether Module are trademarks of SEEQ Technology, Inc.
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MD400135/D
Ether Module - EM2C 10Base-2
Description
The Thin Net module connects the station equipment to a Thin Net (Cheapernet) COAX cable. The on-board 83C92C CMOS COAX transceiver provides the drive current and wave shaping for the transmit signals. It supplies receive signal equalization, collision detection and squelch. 5-6 TX Transmit Data Input. A balanced line receiver input to the module from the MCC for transmit packets. HBE Heartbeat Enable. This input enables the Collision (also called Heartbeat) Test when connected to ground, and disables the test when connected to VEE. SYS GND Ground. System Ground is referenced to VCC. RXI Network Signal Receiver. Connects to the network COAX center conductor, and receives packet data and detects the collision voltage level. TXO Network Signal Transmitter. Connects to the network COAX center conductor through an internal 1N916 diode, and transmits all signals from the MCC to the network. CDS Collision Detect Sense. Connects directly to the network shield, and references the collision detection voltage level.
16
Description of the Pin Functions
PIN # FUNCTION 1-2 CD Collision Output. A balanced 10 MHz differential output to the station equipment when a collision is detected, when excessive data transmission occurs (jabber), or during the Collision Test (Heartbeat Test). 3, 4 11 RX Receive Data Output. Line Driver output to the MCC Receive inputs. VEE Negative Supply. Nominally -9 volts referenced to COAX shield ground. An on-board DC-DC power converter provides -9 volt power for the on-board module , and DC isolation from the station equipment to prevent ground loop current.
9 18
17
20
TOP VIEW
CD + CD - RX + RX - TX + TX -
1 2 3 4 5 6
20
CDS
18 17 16
RXI TXO HBE [1]
SYS GND VCC
9 10
12 11
DM VEE
Figure 2. Ethernet Transceiver Module Pin Configuration
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MD400135/D
Ether Module - EM2C 10Base-2
12 DM Disable module is an active low signal (internal 10K pullup) that may be utilized to turn off the Ether module in the event an alternative transceiver is used, or for power conservation purposes. The TXO signal is disabled when not transmitting to prevent noise on the network. If the COAX cable is shorted or open, no transmitted data appears on the Receiver input. This condition can be detected by the station equipment by running a loopback test. Collision Detection The Collision detector monitors the COAX Center Conductor and senses the voltage conditions created by a collision, where the COAX shield is used as a reference. A collision condition can be detected when two or more stations are transmitting, whether or not the local Transmitter is activated. This is called Receive Mode Collision Detection. The detector signals a collision by sending the 10 MHz oscillator signal through the Collision Pair (CD) to the MCC. The HeartbeatTest is performed at the end of each transmitted data packet to verify the operation of the detector. A collision causes a -2.0 volt average DC level on the center conductor of the network cable. This level passes through a 4-pole Bessel low-pass filter for averaging. The resulting signal is measured by a voltage comparator against the threshold voltage VCD of about -1.5 volts. A collision is indicated when the center conductor average level is more negative than the CDS level by the threshold VCD. The line driver is enabled within 900 ns of the onset of the collision, and the 10 MHz signal is sent to the station equipment. The Heartbeat Test is a short burst of the collision signal generated immediately after the transmission of a packet. This test enables the 10 MHz collision signal for about 1 microsecond starting about 1.1 microseconds after the
Description of the Module Functions
The module has five main functions, as shown in the block diagram. These are the Transmitter; the Collision Detector; the Jabber Timer; the Receiver; and the DC/DC Converter. The on-board SEEQ 83C92C provides all functions except DC/DC conversion and AUI signal isolation. The Transmitter The Transmitter takes differential output signals from the MCC, and outputs these signals at the correct levels to the network. The transmit signal is sent to the module via a balanced differential pair (TX). A squelch circuit prevents the Transmitter Output from responding to noise on the TX pair. The Transmitter has an open-collector current driver output using the VEE supply. Rise and fall times are controlled and set at 25 ns/V to lessen the higher harmonics. Drive current levels are set by a bandgap voltage reference and a internal 1K resistor. An internal diode is also added to reduce COAX loading and capacitance to comply with the ISO and ANSI/IEEE specifications. The transmit squelch circuit blocks signals with pulse widths less than 15 nanoseconds, (negative-going), or with levels of less than -175 millivolts. The squelch circuits turn the Transmitter off at the end of a packet if the signal stays higher than -175 millivolts for more than 190 nanoseconds. See Figure 3, the Transmitter Timing Diagram.
TX
VTSQ t TON t TST
50% t Td
VTSQ t TOFF
TX0
50% t Tf
90% 10% t TID t Tr
TRANSMIT ENABLE
Figure 3. Transmitter Timing
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MD400135/D
Ether Module - EM2C 10Base-2
end of transmission. This test can be disabled for operation with repeaters by connecting the HBE pin to VEE . The Jabber Timer The Jabber Timer monitors the operation of the Transmitter, 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 Transmitter 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 from activating the 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 is output through a differential line driver presenting a balanced signal to the station. The line driver has 4 nanosecond rise and fall times. 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 the Receive Line Driver only when it detects a true signal. This prevents noise triggering the receiver. When a packet is detected, the DC level from the Low-pass Filter becomes more negative than the DC squelch threshold, and the Receiver turns on. The squelch circuit AC timing detects high level signals of more than 225 nanoseconds, and turns the 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 loading when power is on or off. COAX tap capacitance contributed by the Thin Net module is less
RXI t RON RX
50% t t Rd 50% tRf 90% 1 s
RECEIVER SQUELCH LOW-PASS FILTER
DC THRESHOLD
DC THRESHOLD
RECEIVE ENABLE
Figure 4. Receiver Timing
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MD400135/D
Ether Module - EM2C 10Base-2
than 4 pF at 10 MHz, powered and unpowered, not transmitting. CDS, Collision Detection Sense detects the Collision reference level. This is a ground-referenced sense pin. It should be connected directly to the COAX shield to prevent ground-loop interference. The Transceiver assembly includes the DC - DC Converter and a pulse transformer for RX, TX and CD signal isolation.
OSC
D0-D7
8020 8023A NCORE 80C04A 80C03
CLK LPBK * CSN COLL
CD+ CD-
CD+ CD- 39 1% 0.01 F
CDS
D8-D15 CPU A0-A3
MANCHESTER CODE CONVERTER
DATA LINK CONTROLLER
RxC RxD TxEN TxC* TxD
39 1%
CONTROL
RX+ RX- 39 1% 0.01 F TX+ TX- 243 1% 1W 39 1%
RX+ RX-
EM2C
TX+ TX- 243 1% 1W
Figure 5a. Coax Ethernet Transceiver System Connections
5
MD400135/D
CC
SYSTEM GND
V
DM
10 1 2
9 12
V
EE
CDS TXO RXI 20 17
M
MD400135/D
RE 4A 3
TxEN TxC ADUPLX
D0-D7
NETWORK COAX CENTER CONDUCTOR
200
CD + CD - SHIELD 0.01
6
Ether Module - EM2C 10Base-2
Ether Module - EM2C 10Base-2
Absolute Maximum Ratings*
Input Voltage ................................................ 0 to 7V Vcc Operating Temperature ................................ 0 to 70 C Storage Temperature ............................... -20 to 85 C DC Isolation Voltage ........................................ 500V DC AC Isolation Voltage ........................................ 500V AC
Operating Parameters for Module
MIN MAX Input (TAP) Capacitance Crxi+Ctxo Isolation Impedance Ziso 250 4 pf K
*COMMENT: Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Operating Parameters for Isolation Transformer
Primary Open Circuit Inductance ET Constant Rise Time Pri/Sec Leakage Inductance Pri/Sec Capacitance Winding Resistance Turns Ratio Isolation Insulation Resistance OCL ET tRS LL CW/W DCR 1:1 5% 2000 VRMS 10,000 M (DC 250V) 10 0.3 MIN 90 2.1 3 MAX 120 UNIT(S) H V - SV nS H pF
Operating Parameters for DC to DC Converter
MIN TYP MAX Input Voltage Max Input Current Efficiency Ripple Voltage Vn Out
[8]
UNIT(S) V ma % mV P-P
Vin ICC
4.75 60
5 68 91
5.25 30 8
[] 8
120
7
MD400135/D
Ether Module - EM2C 10Base-2
Electrical Characteristics
Symbol ICC1 ICC2 IRXI ITDC ITAC VCD VOD VOC VOB VOA VTSQ CX RRXI RTXO HC2,3 HC4,5 HC6,7 Parameter Supply Current Non Transmitting Supply Current Transmitting
[8]
VCC = 5V 5%, TA = 0 to 70C (See Notes 1, 2 & 3) Min Typ Max 225 300 -2 37 28 -1.49
[2] [1] [7] [7]
Units mA mA A mA mA V mV V mV mV mV pF K K dB dB dB
Receive Input Bias Current (RXI)[3] Transmit Output DC Current Level (TXO) Transmit Output AC Current Level (TXO) Collision Threshold (Receive Mode)[2] Differential Output Voltage (RX, CD) DC Common Mode Output Voltage (RX, CD) AC Common Mode Output[7] Voltage (RX, CD)[2] Transmitter Squelch Threshold (TX) TAP Capacitance[4] Shunt Resistance--Non Transmitting (RXI) Shunt Resistance--Transmitting(TXO) Second and Third Harmonics Fourth and Fifth Harmonics Sixth and Seventh Harmonics
[2] [6] [5]
-1 41 -1.53 -2.0
+25 45 ITDC -1.58 1200 -2.5 40 40
550 -1.5
Idle State Differential Offset Voltage (RX, CD)
-175 100 10 -20 -30 -40
-225 3.0
-300 4.0
Harmonic Content Relative to Fundamental
NOTES 1. VOC has no impact on system performance, since the twisted pair is transformer - isolated. 2. As required to meet ANSI/IEEE 802.3 and ISO 8802-3 specifications. 3. All currents into device pins are positive, all currents out of device pins are negative. All voltages referenced to ground unless otherwise specified. 4. Measured at RXI. Guaranteed through characterization. 5. Current is measured on RXI while first forcing 0 volt and measuring the current, and then forcing -2 volts and measuring the current. Thus:
R=
V 2V = I [ I @ 0V] - [ I @ - 2V]
6. TX is first set to 1 volt differential (DC voltage) to surpass the squelch level. Current is measured on TXO while first forcing 0 volt and measuring the current, and then forcing -2 volts and measuring the current. Calculation is the same as item 5 above. 7. Values shown are internal to the module and are shown to indicate module capability only. 8. Values as shown is for 50% duty cycle, for 100% duty cycle ICC2 = 380 ma.
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MD400135/D
Ether Module - EM2C 10Base-2
Recommended Operating Conditions
Supply Voltage (VCC) ........................................... 5V 5% Ambient Temperature ...................................... 0 to 70C
Switching Characteristics
Symbol tTST tTd tJA tJR tRd tTM tRON tCON tCOFF fCD tCP tHON tHW Parameter
VCC = 5V 5%, TA = 0 to 70C Fig 3 3 8 8 4 15 20 250 Min Typ [1] 1 25 40 500 15 0.5
[2]
Max 2 50 60 750 50 2.0 5 13 20
Units bits ns ms ms ns ns bits bits bits MHz ns s s
Transmitter Startup Delay (TX to TXO)[2] Transmitter Propagation Delay (TX to TXO) Jabber Activation Delay (TX to TXO and CD)[2] Jabber Reset Timeout (TX to TXO and CD) Receiver Propagation Delay (RXI to RX) tTr and tTf Mismatch Receiver Startup Delay (RXI to RX) Collision Turn-On Delay Collision Turn-Off Delay Collision Frequency (CD) Collision Pulse Width (CD)
[2] [2]
4 6 6 6 6 6 6 8.5 35 0.6 0.5
4 7
11.5 70 1.6 1.0 1.5
CD Heartbeat Delay (TX to CD) CD Heartbeat Duration (CD)
NOTES 1. All typicals are given for TA = 25 C, VCC = 5V. 2. As required to meet ANSI/IEEE 802.3 and ISO 8802-3 specifications.
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MD400135/D
Ether Module - EM2C 10Base-2
Timing and Load Diagrams
TX t HON CD t HW
Figure 6. Heartbeat Timing
TX tJA TX0 tJR
CD
Figure 7. Jabber Timing
t RJ
Input Jitter 1ns RX Output Jitter 7 ns Difference 6 ns
Figure 8. Receive Jitter Timing
10
MD400135/D
Ether Module - EM2C 10Base-2 Ordering Information
EM2C -- Ether Module for 10Base-2 Hub and Repeater Applications
Revision History
8/12/96
- Page 12, Mechanical Drawing: - Overall package length reduced from 1.102 0.02 to 1.095 0.030 - Package width changed from 0.990 to 0.975 0.025 - Dimension from pin stand-off to package bottom specified as 0.025 (nom.) - Package thickness changed from 0.415 (max.) to 0.400 (max.) - Lead width tolerance added 0.018 0.003. - Lead row- to-row spacing specification refined, in note 3, replacing "from shoulder to shoulder" to "at seating plane".
2/20/97
- Document revision changed to MD400135/C - Page 12 , Mechanical Drawing - Lead thickness changed from 0.012 to 0.010 0.002.
6/25/97
- Document revision changed to MD400135/D - Page 12 , Mechanical Drawing - Reference to 0.400 Max. has been changed to 0.415 Max - Marking Specifications have been deleted. - Note 7 has been added; Dimensions are measured to point where leads start to narrow.
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MD400135/D
Ether Module - EM2C 10Base-2
20 Pin Module
1.095 0.030
SEEQ Ether Module EM2C (4 Digit Test Date Code)
0.975 0.025
0.010 0.002 0.415 Max.
0.025
Note 7
0.101 0.03 0.100 0.900 0.018 0.003
NOTES 1. All dimensions are in inches. 2. Dimensions do not include mold flash. Allowable mold flash is .010. 3. Dimension is measured at seating plane. 4. Tolerances are .010 unless otherwise specified. 5. For solder dipped leads, thickness will be .020 max. 6. Pins 7, 8, 13, 14, 15, and 19 are missing. 7. Dimensions are measured to point where leads start to narrow.
12
MD400135/D
0.177 0.02
1.020 0.01 Note 3

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