East Coast Datacom DMM-X21 User manual

114.3 ADDRESSES OF STANDARDS ORGANIZATIONS ...................
Page 84.2 FACTORY DEFAULT CHART ..................................
Page 84.1 X.21 INTERFACE CHART .....................................
Page 84.0 - APPENDIX ......................................................
Page 73.5 MODEM (DCE) AND TERMINAL (DTE) CONNECTION ...........
Page 73.4 DEFAULT CONFIGURATION SWITCH SETTINGS ...............
Page 63.3 POWER CONNECTION .......................................
Page 63.2 VOLTAGE SELECTION FUSES ................................
Page 63.1 VOLTAGE SELECTION .......................................
Page 6CHAPTER 3 - INSTALLATION .........................................
Page 52.16 SUB-BHANNEL PORT FIFO OPERATION (J16 - J19) ...........
Page 52.15 MASTER CHANNEL FIFO (J15) ...............................
Page 52.14 FIFO GENERAL OPERATION (J14) ...........................
Page 52.13 DCE / DTE SWITCHES .......................................
Page 52.12 CONTROL (C) LEAD (PORTS 1 - 4) ...........................
Page 52.11 INDICATE (I) LEAD (PORTS 1 - 4) .............................
Page 42.10 CASCADING OR CONCATENATION ...........................
Page 42.9 FALL BACK TIMING ..........................................
Page 42.8 MANUAL DTE/DCE REMOVAL .................................
Page 32.7 INTERNAL CLOCK SELECTION ...............................
Page 32.6 ANTI-STREAMING ............................................
Page 32.5 SUBCHANNEL SERVICE MODES ..............................
Page 32.4 ELECTRICAL INTERFACE ....................................
Page 22.3 CLOCKING MODES ..........................................
Page 22.2 REAR PANEL CONNECTORS AND FUSES .....................
Page 22.1 FRONT PANEL INDICATORS AND SWITCHES ..................
Page 2CHAPTER 2 - BASIC OPERATION .....................................
Page 21.2 THEORY OF OPERATION .....................................
Page 11.1 FUNCTIONAL DESCRIPTION ..................................
Page 1CHAPTER 1 - INTRODUCTION ........................................
TABLE OF CONTENTS

OPERATIONS MANUAL
DIGITAL MIXING MODULE
DMM-X21
14 March 1997
Manufactured By:
East Coast Datacom, Inc.
FOR TECHNICAL SUPPORT CALL:
East Coast Datacom, Inc.
571 Haverty Court, STE N
Rockledge, FL 32955 USA
TEL: [phone] or [phone]
FAX: [phone]
Email: [email protected]
Web Site: www.ecdata.com
PT # 719006-A

SAFETY WARNING
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.
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.
PUBLICATION NOTICE
This manual has been compiled and checked for accuracy. The information in this
manual does not constitute a warranty of performance. E.C.D. reserves the right to
revise this publication and make changes from time to time in the content thereof.
E.C.D. assumes no liability for losses incurred as a result of out-of-date or incorrect
information contained in this manual.
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 1

CHAPTER 1 - INTRODUCTION
1.1 FUNCTIONAL DESCRIPTION
The Digital Mixing Module (DMM-X21) is a network expansion device for X.21 modem sharing
or port sharing applications in broadcast, polled or contention environments. The DMM-X21
allows up to four X.21 devices to share a modem or computer port. Any combination of
terminals and modems may be used in a network environment. Each port of the DMM-X21
conforms to the ITU X.21 standard and may be selected as a DCE or DTE interface.
Ideal for either synchronous or asynchronous network environments, the DMM-X21 is protocol
transparent at data rates up to 1.024Mbps. The DMM-X21 has several user defined modes to
configure clocking for the network and also provides fallback clocking. To prevent or minimize
data transmission errors caused by clock differences throughout the network, 512bit optional
FIFO buffers are provided for each channel. In applications where the master port and the
selected port provide their own clocks, data is clocked into the buffer at the receive clock rate of
the active port and clocked out using the master port transmit clock.
The Control(C) and Indicate(I) leads may be individually selected to follow the modem or forced
active on a per port basis. Fallback timing circuitry is also provided in the DMM-X21.
The DMM-X21 provides optional Anti-Streaming circuitry. Once enabled, Anti-Streaming will
automatically remove a defective terminal or modem from service if the Data / Control criteria is
present for the user predefined selection period.
Housed in a sturdy rack mount metal enclosure and equipped with a 110/220 VAC switch
selectable linear power supply, the DMM-X21 will provide in excess of 100,000 hours of reliable
service.
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 2
X.21 MODEM X.21 MODEM
DMM-X21
TERMINAL
TERMINAL
TERMINAL
SUB-CHANNEL STATUS
PWR TXD RXD
12 3
ACTIVE
STREAM
DMM-X21
EAST COAST
4
1 2 3 4
1 2 3 4
HOST
X.21
LEASED LINE
X.21 MODEM
TYPICAL APPLICATION
Figure 1.1

Set the 110/220 volt select switch for your power requirement. The supplied power
cord plugs into the IEC receptacle. The receptacle also contains a fuse drawer. Two
(2) fuses are located in this compartment. For 110 VAC +/- 10% operation the unit is
equipped with slow blow 320ma Fuses. For 220 VAC +/- 10% operation the unit is
equipped with slow blow 160ma Fuses. Additionally, you will find the Master and
Subchannel female DB-15 connectors.
2.3 CLOCKING MODES
Clocking may be set as Master Channel (Set to DTE) or Channel 4 (Set to DTE) from
the attached DCE. Internal Timing will facilitate user defined operational speeds from
48Khz to 256Khz. Fallback Timing may also be used when the Master Port is connected
to a Front End Processor (FEP) or other DTE device. In this mode, connect Port 1 to the
main clock source. If Port 1 clock fails, fallback to Port 2 clock source will occur. If Port
2 clock source fails, fallback to internal clock will occur. If Port 1 or 2 clock returns, the
DMM-X21 will fall forward to the active DCE clock source with Port 1 having the highest
priority.
A Green LED illuminates when AC Power has been applied. Two adjacent Green LEDs
illuminate in union with individual Green subchannel port activity LEDs and identify
Transmit and Receive data transmissions. Yellow LEDs provide the user with a visual
indication of a streaming DTE (ref. 2.6) Positive latching switches are provided for each
DTE port for isolating or removing a streaming terminal. Each DTE port has its own
switch and operates independently. To disable a subchannel, simply push the switch.
A channel is disabled when the switch is in the outer most position.
2.2 REAR PANEL CONNECTORS AND FUSES
CHAPTER 2 - BASIC OPERATION
2.1 FRONT PANEL INDICATORS AND SWITCHES
1.2 THEORY OF OPERATION
The DMM-X21 allows up to four DCEs or DTEs to share one DCE or DTE
communications link. In a broadcast, polled or contention environment, the typical
Polled Network DMM-X21 operation is as follows:
Data arriving at the DMM-X21's master port is continually broadcast to all subchannel
ports. When one of the DCE or DTE devices answers a poll from the host site, that
device will raise Control (C) or Indicate (I). When (C) is raised, the DMM-X21 will lock
on to that port and allow that DTE device to talk to the modem link. The DMM-X21 will
remain locked onto that port until (C) is dropped. After (C) has dropped, the DMM-X21
will automatically begin scanning the ports until another port raises (C) or (I).
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 3

2.4 ELECTRICAL INTERFACE
The DMM-X21 is ITU V.11, X.21 compliant, utilizing female DB-15 connectors. Refer to
the interface chart in the Appendix for detailed interface information.
2.5 SUBCHANNEL SERVICE MODES
The DMM-X21 incorporates circuitry that enables the user to scan each sub-channel
port. An option is also provided for forcing sub-channel 4 constantly active. In the
forced active mode, data will continue to be broadcast to ports 1, 2 and 3.
2.5.1 SUBCHANNEL SCANNING
Subchannel Scanning will allow equal access to the communications link for all
connected DCE or DTE devices. The subchannels are scanned in sequence (1 - 2 - 3 -
4) and the attached subchannel that raises Control (C) or Indicate (I) will have access to
the communications link. After dropping (C) or (I) the DMM-X21 will continue scanning
in sequential order.
2.5.2 SUBCHANNEL CONTROL(C) TO INDICATE(I) DELAY
Control to Indicate delays of 0, 6.5, 13 and 26ms are user selectable.
2.6 ANTI-STREAMING
2.6.1 AUTOMATIC REMOVAL
The DMM-X21 incorporates circuitry that will (when enabled) automatically remove a
streaming DCE or DTE from service. A streaming terminal is defined as a terminal that
has Control (C) 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 subchannel
activity. Green indicates an active subchannel and Yellow indicates a streaming
subchannel. Once a terminal has gone into the streaming condition (Control continually
high) the DTE will automatically be removed from service until the DTE fault has been
corrected by the user. All other DTE's will continue to be serviced.
2.7 INTERNAL CLOCK SELECTION
The DMM-X21 incorporates circuitry that allows the user to select Internal Clocks. The
selectable rates are 48Khz, 56Khz, 64Khz, 128Khz, 192Khz and 256Khz. Though X.21
is externally timed by the telco provider, the internal clock rates are very useful for
testing and diagnostic purposes.
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 4

2..10 CASCADING OR CONCATENATION
The DMM-X21 supports cascading by utilizing DB-15 Male-to-Male straight through
shielded cables. Subchannel Port 1 should be used as the concatenation port.
2.8 MANUAL DTE/DCE REMOVAL
The DMM-X21 incorporates circuitry that will (when enabled) manually remove a
streaming terminal from service. A streaming terminal is defined as a terminal that has
Control (C) continually high. With Anti-streaming disabled, the associated streaming
DTE will NOT illuminate a Yellow LED on the front of the DMM-X21. If the automatic
anti-streaming circuitry is disabled and a streaming condition occurs, the other DTE
devices will be blocked from accessing the communications link. To correct this
condition, simply push the associated push-button switch for the subchannel that is
streaming. All other DTE's will now continue to be serviced by the DMM-X21.
However, you still need to fix the offending DTE or DCE device that has Control (C) or
Indicate (I) continually raised.
2.9 FALL BACK TIMING
The DMM-X21 incorporates circuitry that allows the user to provide Fall Back Timing to
the network. The circuity allows the user to enable or disable this funtion via Dip
Switch. To enable fall back Timing, go to the dip switch marked S11 and move position
8 to ON. This will provide Port 1 as the main timing source. If Port 1 clock fails, the unit
will automatically switch to Port 2 as the timing source. If Port 2 fails, the unit will
automatically fall back to internal clock as the timing source. If Port 1 clock returns to
service, the unit will automatically switch back to Port 1 timing.
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 5
D
M
M
D
M
M
MODEM
CONNECT TO MASTER PORT
CONNECT TO PORT 1
DB-15 CABLE
CASCADING DIAGRAM
OR F.E.P.

2..16 SUB-BHANNEL PORT FIFO OPERATION (J16 - J19)
This option allows the user to set the internal buffers to operate in two(2) modes;
Mode A) FIFO data path is enabled. Mode B) FIFO data path is bypassed (for
synchronous clocks or if no FIFO chip is present.
2..15 MASTER CHANNEL FIFO (J14)
This option allows the user to set the internal buffers to operate in two(2) modes;
Mode A) FIFO (If present) and ring buffer data path is enabled. Mode B) fifo and ring
buffer are bypassed (for synchronous clocks) or overflow (for isochronous clocks)
2..14 FIFO GENERAL OPERATION (J15)
This option allows the user to set the internal buffers to operate in two(2) modes;
Mode A) FIFOs nearly fill after underrun and nearly empty after overflow (for
asynchronous clocks) Mode B) FIFOs self-center after overrun or overflow (for
isochronous clocks)
2..12 CONTROL (C) LEAD
The DMM-X21 has internal jumpers for Normal or Forced Control (C). This option will
allow Control(C) to operate normally or to be forced inactive when the port is set to
DTE.
2.13 DCE / DTE SWITCHES
Located internally are five sets of two (2) DCE/DTE slide switches directly in front of
each port. Silkscreened on the Printed Wiring Board are DCE and DTE. Slide BOTH
switches to the same position to configure each of the RS-232 ports as a DTE or a DCE
interface.
When set to DCE, the port MUST connect to a DTE device.
When set to a DTE, the port MUST connect to a DCE device.
2..11 INDICATE (I) LEAD
The DMM-X21 has internal jumpers for the Indicate (I) Lead. This option will allow
Indicate(I) to follow Control(C) or to be forced active when the port is set to DCE.
MSD-4 AND MSD-8 INSTALLATION AND OPERATIONS MANUAL
Page 6

Power Connection
Figure 3-1
3.4 DEFAULT CONFIGURATION SWITCH SETTINGS
CHAPTER 3 - INSTALLATION
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 or rear of the product you will find an IEC Power receptacle. This
receptacle contains a fuse drawer. Two (2) fuses are located in this compartment. For
110 VAC +/- 10% operation the unit is equipped with slow blow 5 x 20mm 320ma
(315ma) Fuses. For 220 VAC +/- 10% operation the unit is equipped with slow blow 5 x
20mm 160ma Fuses. Spare fuses may be purchased by calling East Coast Datacom or
by calling the fuse manufacturer; Shurter, Inc. at [phone] or
email: [email protected]
Shurter, Inc. Part #'s are: 315ma = 034.3112 and 160ma = 034.3109
3.3 POWER CONNECTION
Before connecting the DMM-X21 to an AC power source the top cover should be
installed with the supplied #8-32 screws. AC power is supplied to the DMM-X21
through a 2.3m (6.6 ft) 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 or the DMM-X21 Warranty will be void.
MSD-4 AND MSD-8 INSTALLATION AND OPERATIONS MANUAL
Page 7
CAUTION: Disconnect Power Before Servicing
ATTENTION: Couper Le Courant Avant l' Entretien
VORSICHT: Befor Deckung Abnehmen Mach Strom Zu

The DMM-X21 is configured prior to shipping with the Internal Switches set as follows:
1) Master Port - DCE
2) Sub-channel Ports - DTE
3) Timing - External
4) Control (C), Ports 1 through 4 - Enabled
5) Indicate (I), Ports 1 through 4 - Enabled
6) Contol (C) to Indicate (I) Delay - 0ms
7) Anti-Streaming - Disabled
8) Clock Select - 128Khz
9) Fallback Timing - Disabled
10) Port 4 Mode - Disabled (all ports active)
If your system application requires one or more of the default settings to be changed, it
will be necessary to remove the top cover of the DMM-X21. Remove the AC Power
source or Disconnect the AC Power before servicing the unit. Removal of the top cover
is accomplished by using a small Philips screwdriver and removing the four outside
screws. After setting the switches, replace the top cover before applying AC power.
3.5 MODEM (DCE) AND TERMINAL (DTE) CONNECTION
Before applying AC Power to the unit, the DCE and DTE cabling should be connected.
Straight through Male-to-Male DB-15 shielded cables should be used. No crossover
cables are required as each port on the unit is DCE/DTE selectable.
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 8

4.0 - APPENDIX
4.1 X.21 INTERFACE CHART
ITU X.21 INTERFACE CHART (DB-15 CONNECTOR)
NOT USED15
XBYTE TIMING (B-)14
XSIGNAL TIMING (B-)13
XINDICATE (B-)12
XRECEIVE (B-)11
XCONTROL (B-)10
XTRANSMIT (B-)9 --GROUND8
XBYTE TIMING (A+)7
XSIGNAL TIMING (A+)6
XINDICATE (A+)5
XRECEIVE (A+)4
XCONTROL (A+)3
XTRANSMIT(A+)2 --SHIELD1 FROM DTEFROM DCEPIN NAMEPIN NUMBER
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 9
18
15 9
DB-15 FEMALE

4.2 FACTORY DEFAULT CHART
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 10
ON
12 345678 910
DMM-X21 FACTORY DEFAULT / SWITCH GUIDE

4.3 ADDRESSES OF STANDARDS
ORGANIZATIONS
ANSI
American National Standards Institute
1430 Broadway
New York, NY 10018
Telephone: [phone]
EIA
Electronic Industries Association
2001 Eye Street, N.W.
Washington, DC 20006
Telephone: [phone]
FED-STD
General Services Administration
Specification Distribution Branch
Building 197
Washington Navy Yard
Washington, DC 20407
Telephone: [phone]
FIPS
U.S. Department of Commerce
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: [phone]
CCITT
Outside the United States
General Secretariat
International Telecommunications Union
Place des Nations
1121 Geneva 20, Switzerland
Telephone [phone]
In the United States
United States Department of Commerce
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: [phone]
ISO
Outside the United States
International Organization for Standardization
Central Secretariat
1 rue de Varembe
CH-1211 Geneva, Switzerland
Telephone [phone]
Inside the United States
American National Standards Institute
1430 Broadway
New York, NY 10018
Telephone: [phone]
IEEE
The Institute of Electrical and Electronics
Engineers, Inc.
345 East 47th Street
New York, NY 10017
Telephone: [phone]
NBS
National Bureau of Standards
Institute for Computer Sciences and
Technology
Technology Building, Room B-253
Gaithersburg, MD 20899
Telephone: [phone]
CCITT documents may be reached by calling
[phone]
V.35 is a CCITT specification and is
implemented per ISO 2593
The ISO documents are attainable by calling
[phone]
AT&T Bell Publications documents may be
reached by calling [phone] or (800)
432-6600
East Coast Datacom, Inc. DMM-X21 OPERATIONS MANUAL
Page 10

Application
Multiple X.21 Synchronous DCE or DTE
devices contending in a polled environment, to
share one Digital DCE or DTE interface
Capacity
One to Four ITU X.21 devices
Interface
ITU X.21, V.11 using DB-15 female
connectors
Data Rates
Up to 1.024Mbps
Data Format
Data transparent at all data rates
Timing
From Composite (Master) Port or
Sub-channel Port 1
Buffer
Up to 512 bits, FIFO principle with automatic
re-centering
Anti-Streaming
Automatic…Selectable time out intervals
Disable……Selectable via dip switch
Front Panel
Indicators....Power, Send/Receive Data,
Channel Active, Channel
Stream
Switches.....Enable/Disable of each
Subchannel
Power Source
100-120 to 200-220VAC @10%, 50/60Hz,
0.16/0.08A, external 110/220 volt select
switch, IEC Power Inlet, (2) 5mm Fuses
Environmental
Operating Temperature....32º to 122º F (0º
to 50º C)
Relative Humidity.............5 to 95%
Non-Condensing
Altitude............................0 to 10,000 feet
Dimensions
Height ....... 1.75 inches (4.44 cm)
Width ........ 13.35 inches (33.09 cm)
Length ....... 9.00 inches (22.86 cm)
Weight
4.5 pounds (2.1Kg)
Warranty
Three Years, Return To Factory
ORDERING INFORMATION
Model: DMM-X11
Description: 4 Port Digital Sharing Device
W/512bit buffers
INCLUDED WITH EACH UNIT:
1) Operations Manual
2) U.S.A. Grounded Power Cord, Part # 713015
3) Optional Power Cords
A) United Kingdom, Part # 713016
B) Continental Europe, Part # 713017
C) Other: Specify Country on Purchase Order
OPTIONAL ACCESSORIES
1) Spare Data Center Fuses
A) 160ma Fuse, Qty (2)
B) 315ma Fuse, Qty (2)
Page 11
5.0 - TECHNICAL SPECIFICATIONS