East Coast Datacom MSD-4 User manual

OPERATIONSMANUAL
RS-232 MODEM SHARING DEVICE
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Model: MSD-4
4-Port RS-232 Modem Sharing Device
OrderingPartNumber: 101012
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ManufacturedBy:
East Coast Datacom, Inc.
FORTECHNICALSUPPORTCALL:
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East Coast Datacom, Inc.
245 Gus Hipp Blvd., STE 300
Rockledge, FL 32955 U.S.A.
TEL: [phone]
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Email:[email protected]
Web Address: www.ecdata.com
Publication # 719008 Rev - A

CONTENTS
SAFETY WARNINGS / Avertissements de sécurité .................................................................................................................................. 0
CHAPTER 1 - INTRODUCTION ................................................................................................................................................................................. 1
1.1 Functional Description ............................................................................................................................................................................. 1
1.2 Theory of Operation .................................................................................................................................................................................. 2
CHAPTER 2 - BASIC OPERATION AND FUNCTIONS ...................................................................................................................................... 2
2.1 Front Panel Indicators and Switches ................................................................................................................................................. 2
2.2 Front Panel Switches ................................................................................................................................................................................ 2
2.2 Rear Panel Connectors and Fuses ....................................................................................................................................................... 2
2.3 Clocking ........................................................................................................................................................................................................... 2
2.4 Electrical Interface ..................................................................................................................................................................................... 2
2.5 Sub-channel CONTENTION Modes ..................................................................................................................................................... 3
2.5.1 Sub-channel SCANNING Mode ........................................................................................................................................................ 3
2.5.2 Sub-channel PRIORITY Mode ......................................................................................................................................................... 3
2.5.3 Sub-channel SWITCH ON DATA ..................................................................................................................................................... 3
2.6 DATA BROADCAST ONLY APPLICATIONS ...................................................................................................................................... 3
2.7 ANTI-STREAMING ...................................................................................................................................................................................... 3
2.7.1 Automatic DTE Removal ................................................................................................................................................................... 3
2.7.2 Manual DTE Removal ......................................................................................................................................................................... 4
2.7.3 Unexplained Streaming Terminals ............................................................................................................................................... 4
2.8 Dial Modem Support ................................................................................................................................................................................. 4
2.9 Cascading or Concatenation .................................................................................................................................................................. 4
CHAPTER 3 - INSTALLATION .................................................................................................................................................................................. 4
3.1 Voltage Selection ......................................................................................................................................................................................... 4
3.2 Voltage Selection Fuses ............................................................................................................................................................................ 4
3.3 Power Connection ...................................................................................................................................................................................... 5
3.4INTERNAL DIP SWITCH AND PIN-HEADER SETTINGS .......................................................................................................... 5
3.4.1SW1 Dip Switch Settings ............................................................................................................................................................ 5
3.4.1.2Anti-Streaming (SW1-4) ....................................................................................................................................................... 5
3.4.2.2 Channel Service Modes (SW1-5) ..................................................................................................................................... 5
3.4.2.3 Frame to Signal Ground (SW1-6) .................................................................................................................................... 5
3.5SUB-CHANNEL CONTENTION MODES ........................................................................................................................................... 6
RTS/CTSOperationtoSub‐ChannelContention(HandShaking) ............................................................................................. 6
OR‐MODEOperation(Systemdoesn’tcareaboutRTSorDTR.Anyportdatagetsthru) .......................................... 6
3.6MASTER PORT OPTIONS ...................................................................................................................................................................... 6
3.7SUB-CHANNEL PORT OPTIONS ......................................................................................................................................................... 6
4.0 - APPENDIX ............................................................................................................................................................................................................... 8
4.1 Serial Port Pinouts ..................................................................................................................................................................................... 8
OVERVIEW, MSD-4 FRONT AND REAR VIEWS ................................................................................................................................................ 9
5.0–TECHNICAL SPECIFICATIONS .................................................................................................................................................................... 1 0 

SAFETYWARNINGS
Always observe standard safety precautions during installation, operation and maintenance of this
product. To avoid the possibility of electrical shock, be sure to disconnect the power cord from the power
source before you remove the IEC power fuses or perform any repairs.
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AVERTISSEMENTSDESÉCURITÉ
Respectez toujours les précautions de sécurité standard lors de l'installation, du fonctionnement et de la
maintenance de ce produit. Pour éviter tout risque de choc électrique, assurez-vous de débrancher le
cordon d'alimentation de la source d'alimentation avant de retirer les fusibles d'alimentation CEI ou
d'effectuer toute réparation.
FCCCLASSAINFORMATION
This device complies with part 15 of the FCC Rules. Operation is subject to the following two
conditions: (1) This device may not cause harmful interference, and (2) this device must accept
any interference received, including interference that may cause undesired operation.
Changes or modifications to this product not expressly approved by East Coast Datacom, Inc.
could void the user's authority to operate the equipment.
PROPRIETARYNOTICE
The information contained herein is proprietary to East Coast Datacom, Inc. Any reproduction or
redistribution of this publication, in whole or in part, is expressly prohibited unless written authorization
is provided by East Coast Datacom, Inc.
WARRANTYNOTICE
WARRANTIES: East Coast Datacom, Inc. (hereafter referred to as E.C.D.) warrants that its equipment is
free from any defects in materials and workmanship. The warranty period shall be three (3) years from
the date of shipment. E.C.D.'s sole obligation under its warranty is limited to the repair or replacement of
defective equipment, provided it is returned to E.C.D., transportation prepaid, within a reasonable period.
This warranty will not extend to equipment subjected to accident, misuse, alterations or repair not made
by E.C.D. or authorized by E.C.D. in writing.
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CAUTION: FOR CONTINUED PROTECTION FROM RISK OF FIRE,
REPLACE ONLY WITH SAME TYPE AND RATING FUSE.
ATTENTION: POUR UNE PROTECTION CONTINUE CONTRE LES
RISQUES D'INCENDIE, REMPLACEZ UNIQUEMENT AVEC UN
MÊME TYPE ET UN FUSIBLE DE QUALITÉ.
CAUTION: RISKOFELECTRICSHOCK: GROUNDED CONDUCTOR (NEUTRAL) PROVIDED
WITH OVERCURRENT PROTECTION. TEST COMPONENTS BEFORE TOUCHING.
ATTENTION: RISQUEDECHOCÉLECTRIQUE: CONDUCTEUR MIS À LA TERRE (NEUTRE)
ÉQUIPÉ D'UNE PROTECTION CONTRE LES SURINTENSITÉS. TESTEZ LES COMPOSANTS
AVANT DE TOUCHER.

USER MANUAL, MSD-4, PT# 101012
Page | 1EAST COAST DATACOM, INC.

CHAPTER 1 - INTRODUCTION

1.1FUNCTIONALDESCRIPTION
The MSD-4 provides the network manager with a cost-effective means of expanding existing,
leased line polled networks without adding computer ports or communications links. With the
MSD-4, up to four terminals can share the same port and communications link using the
contention and control protocols normally resident in the host hardware and software. Once
installed, system and network efficiency are increased through higher host processor utilization
coupled with the significant decrease in idle time between host / terminal traffic sessions.
Ideal for either synchronous or asynchronous network environments, the MSD-4 is protocol
transparent at data rates up to 19.2Kbps. Data arriving at the Master Port is continually
broadcast to all Sub-channels. The user is presented with two modes of operation for terminal
access. The first mode is the attached terminal device(s) that raises the RTS control signal is
automatically given control of the MSD channel until data transmission is complete. The second
mode is the attached terminal device(s) that transition data from Mark to Hold is automatically
given control of the MSD until data transmission is complete. This is commonly called the “OR”
mode of operation. Clocking in both modes of operation is accomplished from the attached
Modem. The MSD-4 may also be used in broadcast only applications as ref. in Section 2.6.
The MSD-4 incorporate optional Anti-Streaming circuitry. If enabled, Anti-Streaming will
automatically remove a defective terminal from service if the Data / Control criteria is present
for the user predefined clock selection period.
Housed in a sturdy metal enclosure and equipped with a 110/220 VAC switch selectable linear
power supply, the MSD-4 will provide in excess of 100,000 hours of reliable service.
Figure1‐TYPICALAPPLICATION

USER MANUAL, MSD-4, PT# 101012
Page | 2EAST COAST DATACOM, INC.
1.2THEORYOFOPERATION
In a polled or contention environment the typical MSD operation is as follows:
Data arriving at the MSD's master port is continually broadcast to all of the MSD-4 sub-channel
ports. When one of the DTE devices answers the poll from the host site, that DTE device will
raise RTS (Request To Send). When RTS is raised the MSD-4 scanner circuitry will lock on to that
port and allow that attached DTE device to communicate with the modem link. The MSD will
remain locked onto that port until RTS is dropped and CTS (Clear To Send) is dropped from the
modem. After RTS and CTS have dropped, the MSD will automatically begin scanning the ports
until another port raises RTS.
OPTIONALLY: The “OR-MODE” of operation may be selected and the contention mode with any
DTE device that the DATA lead transitions from Mark to Hold will have access to the Master
Port.(the user system software must only allow one device at a time communicate)
CHAPTER 2 - BASIC OPERATION AND FUNCTIONS
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2.1FRONTPANELINDICATORSANDSWITCHES
A Green LED illuminates when AC Power has been applied. Four adjacent Green LEDs illuminate
and identify CTS, DCD, RXD and TXD on the Master Ports RS-232 signal status. Sub-channel Ports
A thru D Active LED’s are also green and only one of the four LED’s will ever illuminate at a single
time, when a sub-channel is active. Yellow LEDs are provided as a visual indication of a
streaming sub-channel, the LEDs illuminate only if anti-streaming is enabled.
2.2FRONTPANELSWITCHES
Positive latching switches are provided for each sub-channel Port A thru D for isolating or
removing attached terminals. To disable a sub-channel simply push the switch, so it is in the
outer most position. NOTE: The switch disables the ability of the sub-channels Pin 2 TXD to
transmit back to the Master Port. Pin 3 RXD from the Master Port is always sent out to all sub-
channels. This feature is by design for data broadcast applications and data is always outbound.
2.2REARPANELCONNECTORSANDFUSES
Located on the rear of the product you will find an IEC Power Receptacle. The supplied power
cord plugs into this receptacle. This receptacle also contains a fuse drawer.
2.3CLOCKING
The MSD-4 derives clocking from the attached Modem or DCE.
2.4ELECTRICALINTERFACE
The MSD-4 is EIA RS-232 (CCITT V.24) compliant using female DB-25 connectors.

USER MANUAL, MSD-4, PT# 101012
Page | 3EAST COAST DATACOM, INC.
2.5SUB‐CHANNELCONTENTIONMODES
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2.5.1 Sub-channel SCANNING Mode
The ScanningMode will allow equal access to the communications link for all connected DTE
devices. The Sub-channels are scanned in sequence (1 - 2 - 3 - 4) and the attached sub-channel
DTE that raises RTS will have access to the communications link. After dropping RTS the MSD
will continue scanning in sequential order.
2.5.2 Sub-channel PRIORITY Mode
The PriorityMode allows the user to have channel 1 as the highest priority channel to service the
communications link. The Sub-channels are continually monitored. If channel 2 or 3 raises RTS
and transmits data and then drops RTS, sub-channel 1 will have the highest priority over the
next port that raises RTS, (if sub-channel 1 has information to transmit). This will allow a DTE
that has more important information to send or retrieve from the host a higher priority.
2.5.3 Sub-channel SWITCH ON DATA
The Switch on Data Mode allows an attached sub-channel DTE device to access the Master Port
when data is sent. In this mode of operation, the network must be disciplined as that no two sub-
channels can communicate back to the host at the same time.
2.6DATABROADCASTONLYAPPLICATIONS
The MSD-4 may be used in Data/Clock Broadcast applications. This can be accomplished by
several methods. One: Disable the Front Panel switches and RXD and Clock from the Master Port
will always continue outbound to all sub-channels. And data cannot be sent back to the Master
Port. Two: Remove Pin 2 TXD from the attached sub-channel cables, data and clock will always
be broadcast to all sub-channels.
NOTE: The front Panel LED’s will show RXD and DCD if sent by the Master Port to the sub-
channels. The PortActiveLED’s will not illuminate in a broadcast only application.
2.7ANTI‐STREAMING
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2.7.1 Automatic DTE Removal
The MSD-4 incorporates circuitry that will (when enabled) automatically remove a streaming
terminal from service. A streaming terminal is defined as a terminal that has RTS high longer
than the user predefined anti-stream timer has been set. Upon installation, the user can set or
actually fine tune the timer to your network requirements. Each channel has a Green and a
Yellow LED to indicate sub-channel activity. Green indicates an active sub-channel and Yellow
indicates a streaming sub-channel. Once a terminal has gone into the streaming condition (RTS
continually high) the DTE will automatically be removed from service until the DTE fault has

USER MANUAL, MSD-4, PT# 101012
Page | 4EAST COAST DATACOM, INC.
been corrected by the user. All other DTE's will continue to be serviced by the MSD. NOTE:Anti‐
streamingisnotfunctionalinOr‐Mode
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2.7.2 Manual DTE Removal
The MSD-4 incorporate circuitry that will manually remove a terminal from service. Simply push
the associated push-button switch for the sub-channel that you wish to remove from service on
the front panel. All other sub-channels will continue to operate as normal.
2.7.3 Unexplained Streaming Terminals
Many different types of terminals have been manufactured over the years. A typical problem is
unexplained lockup or lockout problems. The most common cause is when, four terminals are
running just fine and when one of the terminals is powered down, the remaining terminals are
locked out of service. This may be explained by a missing or incorrect Termination Resistor that
has been overlooked by your terminal manufacturer. This is the main reason that Anti-
Streaming circuitry has been designed into the MSD-4 as well a 22k pull-down resistor is on each
sub-channel’s RTS leads, for long unterminated cables.
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2.8DIALMODEMSUPPORT
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The MSD-4 support dial modem applications by connecting the DTR jumper pin for each DTE
port. The jumper pin enables/disables the DTR signal to each DTE sub-channel. If a dial modem
is used with terminals, all DTR jumpers must be enabled.(JP15-JP-18.
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2.9CASCADINGORCONCATENATION
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The MSD-4 supports cascading and the user simply needs to use DB-25 Male to Male straight
through shielded cables. Sub‐channelPort1 should be used as the concatenation port.
CHAPTER 3 - INSTALLATION
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3.1VOLTAGESELECTION
It is very important to check that the unit is set to the correct voltage setting for your application
before applying AC power. Located on the rear of the unit you will find a rotary 110/220 VAC
switch. Using a coin or small screwdriver, gently turn the switch to the appropriate power
position as required for your installation (110 or 220 VAC).

3.2VOLTAGESELECTIONFUSES
Located on the back of the product you will find an IEC Power receptacle. This receptacle
contains a fuse drawer. Two (2) fuses are located in this compartment.
Little Fuse Part #: 0.160ma = 218.160 for 110VAC or 0.080ma = 218.080 for 220VAC
Shurter, Inc. Part #: 0.160ma = 034.3109 for 110VAC or 0.080ma = 034.3106 for 220VAC
Disconnect Power Before Servicing - Coupez l'alimentation avant l'entretien

USER MANUAL, MSD-4, PT# 101012
Page | 5EAST COAST DATACOM, INC.
3.3POWERCONNECTION

Before connecting the MSD-4 to an AC power source the top cover should be installed with the
supplied #4-40 screws. AC power is supplied to the MSD-4 via the supplied power cord
terminated by a grounded 3-prong plug. Select an appropriate location accessible to and within
four to five feet of an AC outlet. The AC Power source MUST be grounded.
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3.4INTERNALDIPSWITCHANDPIN‐HEADERSETTINGS

Remove the power to set the dip switch and jumper settings.
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3.4.1SW1DipSwitchSettings
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The following options are supported on SW1 Dip Switch
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3.4.1.2Anti‐Streaming(SW1‐4)
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Anti‐Streaming is set with Dip Switches SW11‐4 as shown in the chart below.
To Disable Anti‐Streaming, set dip switches SW1,1‐4 all to the OFF position.

Anti‐StreamingTime‐out
SW‐1SW‐2SW‐3SW‐4Time(Sec)
OFFOFFOFFON0.02
ONOFFOFFON0.04
OFFONOFFON0.08
ONONOFFON0.3
OFFOFFONON1
ONOFFONON5
OFFONONON20
ONONONON40
OFFOFFOFFOFFDisabled

3.4.2.2ChannelServiceModes(SW1‐5)

Dip Switch position SW1‐5 provides the sub-channel service modes of operation. The ON
position provides SEQUENTIALSCANNING. The OFF position provides the PRIORITYMODE, with
sub-channel 1 having the highest priority over all other attached Sub-channels.

3.4.2.3FrametoSignalGround(SW1‐6)

Dip Switch position SW1‐6 provides the following functions:
ON (or up) RS-232 DB-25 Pin # 1, (Frame Ground) Connected to Pin # 7, (Signal Ground).
OFF (or down) RS-232 DB-25 Pin # 1, (Frame Ground) Not Connected Pin # 7, (Signal Ground).

USER MANUAL, MSD-4, PT# 101012
Page | 6EAST COAST DATACOM, INC.

3.5SUB‐CHANNELCONTENTIONMODES

To set the MSD-4 to operate in “RTS” or the “OR-MODE”, set as shown below for Jumpers JP11,
JP12 & JP13. MovethePinHeaderJumpers located on the printed circuit card.
RTS/CTSOperationtoSub‐ChannelContention(HandShaking)

JP11, Pins 2-3
JP12, JP13 Pins 1-2
Optional: DTR & RTS Required to Switch Sub-Channels
JP15, JP16, JP17, JP18
1-2 RTS only
2-3 RTS & DTR
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OR‐MODEOperation(Systemdoesn’tcareaboutRTSorDTR.Anyportdatagetsthru)

JP11 Pins 1-2
JP12, JP13 Pins 2-3
3.6MASTERPORTOPTIONS

JP5 CTS Master Port Operation
1-2 Force
2-3 Pass (Normal)
JP6 RTS Master Port Operation
1-2 RTS to Master is forced ON
2-3 Normal RTS to Master port. Any Sub-channel port RTS gives RTS to master.
JP7 DTR Master Port Operation
1-2 DTR to Master is turned ON if any DTR from User ports is turned ON.
2-3 DTR to Master is for forced on.
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3.7SUB‐CHANNELPORTOPTIONS

JP1, JP2, JP3, JP4 CTS Sub-Channel Control(per port control)
1‐6CTStouserportfollowsRTS
NOTE:InthissettingIftheattachedTerminal(DTE)raisesRTS,CTSislocallysentbacktotheDTE
fromtheMSDsub‐channelportyouareattachedtoontheMSD.
2‐5CTStouserportfollowsRTSfromuserport.
NOTE:Inthissetting2‐5,RTSfromsub‐channelportflowsthruMSDmasterporttoattached
modem,thenthemodemsCTSflowsbackthrutheMSDtotheattachedTerminal(DTE)
3‐4CTStouserportisforcedON



USER MANUAL, MSD-4, PT# 101012
Page | 7
EAST COAST DATACOM, INC.

OVERVIEW,MSD‐4PCB&SWITCHSETTINGS
Figure2‐PCBOVERVIEWMSD‐4 