Black Box LD485S-MP User manual

CUSTOMER
SUPPORT
INFORMATION
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Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
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AUGUST 1999
ME742A-R3
ME742C-R3
BC00703
FA520A-R2
RS-232/RS-485 Synchronous
Multipoint Line Driver (LD485S-MP)
LD485S-MP
RTS CD TD RD PWR
DLB LLB TEST

1
TRADEMARKS
TRADEMARKS USED IN THIS MANUAL
Any trademarks used in this manual are acknowledged to be the property of the
trademark owners.

2
LD485S-MP
FEDERAL COMMUNICATIONS COMMISSION
AND
CANADIAN DEPARTMENT OF COMMUNICATIONS
RADIO FREQUENCY INTERFERENCE STATEMENTS
This equipment generates, uses, and can radiate radio frequency energy and if not
installed and used properly, that is, in strict accordance with the manufacturer’s
instructions, may cause interference to radio communication. It has been tested
and found to comply with the limits for a Class A computing device in accordance
with the specifications in Subpart J of Part 15 of FCC rules, which are designed to
provide reasonable protection against such interference when the equipment is
operated in a commercial environment. Operation of this equipment in a
residential area is likely to cause interference, in which case the user at his own
expense will be required to take whatever measures may be necessary to correct the
interference.
Changes or modifications not expressly approved by the party responsible for
compliance could void the user’s authority to operate the equipment.
This digital apparatus does not exceed the Class A limits for radio noise emission from digital
apparatus set out in the Radio Interference Regulation of Industry Canada.
Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites
applicables aux appareils numériques de la classe A prescrites dans le Règlement sur le
brouillage radioélectrique publié par Industrie Canada.

3
NOM STATEMENT
NORMAS OFICIALES MEXICANAS (NOM)
ELECTRICAL SAFETY STATEMENT
INSTRUCCIONES DE SEGURIDAD
1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de
que el aparato eléctrico sea operado.
2. Las instrucciones de seguridad y operación deberán ser guardadas para
referencia futura.
3. Todas las advertencias en el aparato eléctrico y en sus instrucciones de
operación deben ser respetadas.
4. Todas las instrucciones de operación y uso deben ser seguidas.
5. El aparato eléctrico no deberá ser usado cerca del agua—por ejemplo, cerca
de la tina de baño, lavabo, sótano mojado o cerca de una alberca, etc..
6. El aparato eléctrico debe ser usado únicamente con carritos o pedestales que
sean recomendados por el fabricante.
7. El aparato eléctrico debe ser montado a la pared o al techo sólo como sea
recomendado por el fabricante.
8. Servicio—El usuario no debe intentar dar servicio al equipo eléctrico más allá
a lo descrito en las instrucciones de operación. Todo otro servicio deberá ser
referido a personal de servicio calificado.
9. El aparato eléctrico debe ser situado de tal manera que su posición no
interfiera su uso. La colocación del aparato eléctrico sobre una cama, sofá,
alfombra o superficie similar puede bloquea la ventilación, no se debe colocar
en libreros o gabinetes que impidan el flujo de aire por los orificios de
ventilación.
10. El equipo eléctrico deber ser situado fuera del alcance de fuentes de calor
como radiadores, registros de calor, estufas u otros aparatos (incluyendo
amplificadores) que producen calor.
11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del
tipo descrito en el instructivo de operación, o como se indique en el aparato.

4
LD485S-MP
12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización
del equipo no sea eliminada.
13. Los cables de la fuente de poder deben ser guiados de tal manera que no
sean pisados ni pellizcados por objetos colocados sobre o contra ellos,
poniendo particular atención a los contactos y receptáculos donde salen del
aparato.
14. El equipo eléctrico debe ser limpiado únicamente de acuerdo a las
recomendaciones del fabricante.
15. En caso de existir, una antena externa deberá ser localizada lejos de las lineas
de energia.
16. El cable de corriente deberá ser desconectado del cuando el equipo no sea
usado por un largo periodo de tiempo.
17. Cuidado debe ser tomado de tal manera que objectos liquidos no sean
derramados sobre la cubierta u orificios de ventilación.
18. Servicio por personal calificado deberá ser provisto cuando:
A: El cable de poder o el contacto ha sido dañado; u
B: Objectos han caído o líquido ha sido derramado dentro del aparato; o
C: El aparato ha sido expuesto a la lluvia; o
D: El aparato parece no operar normalmente o muestra un cambio en su
desempeño; o
E: El aparato ha sido tirado o su cubierta ha sido dañada.

5
CONTENTS
Contents
Section Page
1. Specifications ..........................................................................................................6
2. Introduction ............................................................................................................9
2.1 Application ..................................................................................................10
2.2 Front-Panel Indicators and Buttons............................................................11
2.3 Back-Panel Connectors................................................................................12
3. Configuration ........................................................................................................13
3.1 Switches ........................................................................................................15
3.1.1 Baud Rate ..............................................................................................15
3.1.2 Transmit Data Clock ............................................................................16
3.1.3 Node Termination (Switch 7) ............................................................17
3.2 Jumpers ........................................................................................................17
3.2.1 Constant Carriers or Switched Modes ................................................17
3.2.2 RTS/CTS Delay ....................................................................................18
3.2.3 Full or Half-Duplex Operation ............................................................19
3.2.4 Tying Signal Ground to Frame Ground..............................................19
4. Installation ............................................................................................................20
5. Test Modes ............................................................................................................21

6
LD485S-MP
1. Specifications
Terminal Interface — EIA RS-232-C (CCITT V.24/V.28) configured as DCE
serial synchronous internal/external/recovered TX data
clock
Line Interface — EIA RS-485 twisted pair (26 AWG minimum), DC
continuity required
Data Rates — 1200, 2400, 4800, 9600, 19,200, 38,400, 56,000, 64,000,
112,000, or 128,000 bps
Operating Modes — 2-wire half duplex, 4-wire full or half duplex; point-to-
point or multipoint; normal or line/digital loopback;
Constant Carrier or Switched Mode
Pins Supported — RS-232-C: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 17, 20, 24; RS-485:
TX A, TX B, RX A, RX B
RTS/CTS Delay — 0, 11, 50, or 160 ms
Connectors — (1) DB25 female, (1) 4-screw terminal block
Indicators — 5 LEDs: TX, RX, RTS, CD, PWR
MTBF — 100,000 hours (approximately)
Operating
Temperature — 32 to 122°F (0 to 50°C)
Storage
Temperature — -4 to +158°F (-20 to +70°C)
Humidity — 15 to 90% relative humidity, non-condensing
Power — Wallmount transformer, 115 VAC/100 mA or
230 VAC/50 mA
Size — Standalone: 1.8"H x 5.5"W x 8.5"D (4.5 x 13.9 x 21.5 cm);
Rackmount: 4.7"W x 7.4"D (11.9 x 18.8 cm)
Weight — Standalone, unit only: 1 lb. (0.45 kg); Standalone,
including transformer: 1.5 lb. (0.68 kg); Rackmount:
0.5 lb. (0.23 kg)

7
CHAPTER 1: Specifications
Transmission
Distance — (4-wire point-to-point, 26-AWG twisted pair)
Speed (bps) Distance
1200 4 miles (6.4 km)
2400 3 miles (4.8 km)
4800 2.3 miles (3.68 km)
9600 1.7 miles (2.72 km)
19,200 1.2 miles (1.92 km)
38,400 0.9 mile (1.44 km)
56,000 0.8 mile (1.28 km)
64,000 0.75 mile (1.2 km)
112,000 0.55 mile (0.88 km)
128,000 0.35 mile (0.56 km)
Interface Pinouts —
RS-485
Pin Name
TX A
TX B Transmit Data Pair
RX A
RX B Receive Data Pair

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LD485S-MP
RS-232-C
Pin Name
1 Protective Ground (FG)
2 Transmit Data (TD)
3 Receive Data (RD)
4 Request To Send (RTS)
5 Clear To Send (CTS)
6 Data Set Ready (DSR)
7 Signal Ground (SG)
8 Receive Line Signal Detector (CD)
9 Aux + power (+12V through 560 ohms)
10 Aux - power (-12V through 560 ohms)
15 Transmitter Signal Element Timing (TC)
17 Receiver Signal Element Timing (RC)
20 Data Terminal Ready (DTR)
24 DTE Transmitter Signal Element Timing

9
CHAPTER 2: Introduction
2. Introduction
The RS-232 Synchronous Multipoint Line Driver provides short-haul synchronous
data communication over customer-owned twisted-pair cable. It’s available as a
standalone unit (Part Number ME742A-R3) or a rackmount card (Part Number
ME742C-R3). The rackmount version is functionally identical to the standalone
unit, but it fits in a rackmount chassis that holds up to 16 cards. Each Line Driver
comes with a 6-ft. DB25 male to DB25 male RS-232 extension cable and a DB9
female to DB25 male adapter.
The LD485S has an RS-232 port (configured as DCE) that connects to a host
computer or terminal (DTE), and a 4-screw terminal block for RS-485
communication over a 2- or 4-wire line. Transmission can be two-wire half duplex,
or four-wire half/full duplex. There are a variety of switch-selectable baud rates
ranging from 1200 to 128,000 bps.
A group of LEDs on the unit’s front panel indicate flow-control status (TX, RX,
RTS, CD). Three pushbuttons on the front panel are used to perform line and
digital loopback testing. A number of options are configurable via internal switches
or jumpers:
• Data rate
• Constant Carrier/Switched Mode with selectable RTS/CTS delay
• Full/half duplex
• TX data clock select
• Node termination
• Frame ground/signal ground

10
LD485S-MP
2.1 Application
Two or more Line Drivers can be set up for point-to-point or multipoint
applications as shown in Figures 2-1 and 2-2. A multidrop network can
accommodate up to 64 devices.
Figure 2-1. Point-To-Point Synchronous Application.
Figure 2-2. Multipoint Synchronous Application.
IBM 3274
Controller
PC with 3270
Emulation PC with 3270 Emulation
IBM Mainframe
Master
2- or 4-wire
Cable
Node Node
Node
IBM Mainframe
2- or 4-wire
Cable
IBM 3274
Controller

11
CHAPTER 2: Introduction
2.2 Front-Panel Indicators and Buttons
The front panel of the RS-232 Synchronous Multipoint Line Driver has five status
indicators (LEDs) as follows:
TD Will light when data is transmitted by the local attached RS-232 device
(pin 2 is active).
RD Will toggle as data is received from the remote RS-232 device (pin 3 is
active).
RTS Will light when RS-232 device raises RTS to request data transmission (pin
4 is active).
In Constant Carrier Mode the RTS LED will always be on, causing the
remote Line Driver’s CD light to always be on.
NOTE
Constant Carrier Mode pertains to full duplex or simplex operation only.
In Switched Mode the RTS LED will only be on if RTS is asserted, causing
the remote Line Driver’s CD LED to light.
CD Indicates status of remote Line Driver’s RTS signal.
If the remote Line Driver is in Constant Carrier Mode, the local Line
Driver’s CD LED will always be on.
If the remote Line Driver is in Switched Mode, the local Line Driver’s CD
LED will light when the remote device asserts RTS.
PWR Indicates the presence of power.
Three pushbuttons are located on the front panel used for various testing
operations as follows:
TST End-To-End Continuity Test (button provides test pattern for all test
operations)
LLB Line Loopback Test
DLB Digital Loopback Test
See Chapter 5 for instructions on performing each test.

12
LD485S-MP
2.3 Back-Panel Connectors
Two connectors are located on the LD485S’s rear panel:
• One DB25 female connector, configured as DCE; connects the line driver to
an RS-232 DTE device.
• One 4-screw terminal block: for RS-485 communication between two or more
Line Drivers over two or four wires.

13
CHAPTER 3: Configuration
3. Configuration
Before you install the Line Driver, configure it to work in your application.
Figure 3-2 shows a layout of the printed circuit board and the location of the
jumpers and switches. Each option is discussed in detail in Sections 3.1 and 3.2.
Figure 3-1. Inter-Connect Wiring Diagram.
THESE UNITS
ARE SLAVES
IF MULTI-POINT
THESE UNITS
ARE SLAVES
IF MULTI-POINT
2-WIRE CONNECTION
(HALF DUPLEX)
4-WIRE CONNECTIONS
(FULL DUPLEX)
MASTER UNIT
IF MULTI-POINT
MASTER UNIT
IF MULTI-POINT
TX-A
TX-B
RX-A
RX-B
RX-A
RX-B
TX-A
TX-B
RX-A
RX-B
TX-A
TX-B
TX-A
TX-B
RX-A
RX-B
RX-A
RX-B
TX-A
TX-B
RX-A
RX-B
TX-A
TX-B

14
LD485S-MP
Figure 3-2. Printed Circuit Board Layout.
J1
P2
NOTE:
DEFAULT JUMPER AND SWITCH SETTINGS SHOWN
PWR
RD
TD
CD
RTS
TST
LLB
DLB
TRANSMIT
CLOCK
SELECT
S6
O
NO
F
F
4
3
2
1
W1
W3
RXB
RXA
TXB TXA TB1
P1
O
F FO
N
S7
1
2
3
4
2
1
BAUD
RATE
SETTINGS
O
NO
F
F
8
7
6
5
4
3
2
1
S5
S4
O
NO
F
F
4
3
2
1
50ms
W2
11ms
0ms RTS/CTS
160ms
E
D
C
B
A
Constant Carrier
SWITCH MODE-JUMPER IN ONE OF
FIVE RTS/CTS DELAY POSITIONS

15
CHAPTER 3: Configuration
3.1 Switches
Three options are user-configurable via the internal switches:
• Baud rate
• Transmit data clock
• Node termination
3.1.1 B AUD R ATE
Ten switch-selectable data rates are available: 1200, 2400, 4800, 9600 (factory
setting), 19,200, 38,400, 56,000, 64,000, 112,000, or 128,000 bps.
The maximum transmission distance is dependent on the data rate selected. The
typical range for data transmission is 4 miles at 1200 bps and 0.35 miles at 12,800
bps. Refer to the table in Chapter 1 for a list of baud rates and maximum
transmission distances.
NOTE
The baud rate should be set to match the rate of the attached DTE.
Table 3-1. Baud Rate Settings (Switches 4 & 5)
Baud Switch 4, Position Switch 5, Position
Rate (bps) 4 3 2 1 8 7 6 5 4 3 2 1
1200 ON OFF OFF ON ON ON ON ON ON ON OFF ON
2400 OFF ON ON ON ON ON OFF ON ON OFF OFF ON
4800 OFF OFF ON ON ON ON OFF ON ON OFF OFF ON
9600* OFF OFF OFF ON ON ON OFF ON ON OFF OFF ON
19,200 OFF OFF OFF OFF ON ON OFF ON ON OFF OFF ON
38,400 OFF OFF OFF OFF ON ON OFF ON OFF ON OFF OFF
56,000 OFF OFF OFF OFF ON ON ON ON OFF OFF ON OFF
64,000 OFF OFF OFF OFF ON ON OFF ON OFF OFF ON OFF
112,000 OFF OFF OFF OFF ON OFF ON ON OFF OFF OFF ON
128,000 OFF OFF OFF OFF OFF ON ON OFF OFF OFF ON OFF
* factory setting

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LD485S-MP
3.1.2 T RANSMIT D ATA C LOCK
Data timing is synchronized among all connected devices in one of three ways:
• Internal Clock (factory setting)
• Recovered Clock
• External Clock
Internal Clock — Line Driver generates transmit data clock and presents
clock to attached DTE via Pin 15. The DTE then presents
synchronized data to the LD485S on Pin 2.
Recovered Clock — Transmit data clock is presented to the DTE on Pin 15,
synchronized with timing of data received from the remote
device. The DTE then presents synchronized data to the
LD485S on Pin 2.
External Clock — Clocking is determined by local DTE. The clock is
presented to the Line Driver on Pin 24, and returned on
Pin 15. The DTE then presents synchronized data to the
LD485S on Pin 2.
Table 3-2. Transmit Clock Options (Switch 6)
Switch 6, Position
Pin 15 Clock Source 4 3 2 1
Internal* ON OFF ON OFF
Recovered ON OFF OFF ON
External ON ON OFF OFF
Pin 15 Disabled OFF — — —
*factory setting
To achieve a master clock, one of the Line Drivers should be set to internal or
external clocking and the other Line Driver(s) set to recovered clock.

17
CHAPTER 3: Configuration
3.1.3 N ODE T ERMINATION (S WITCH 7)
You can select whether or not the termination network for the receiver is
connected to the line. Terminating the devices on the extreme ends of the line
reduces distortion and improves overall signal quality in most applications. The
factory setting is with Switch 7 in the TERM position.
In point-to-point applications, both devices should have the node termination
option enabled.
In multipoint applications, only the two devices at the extreme ends of the line
should be terminated. Configuring any of the other devices on the line for node
termination would result in an increase in the amount of distortion and possible
data errors.
3.2 Jumpers
Four options are user-configurable via internal jumpers:
• Constant Carrier/Switched Mode - Jumper W2
• RTS/CTS Delay (for Switched Mode) - Jumper W2
• Full/Half Duplex - Jumper W3
• Frame Ground/Signal Ground - Jumper W1
3.2.1 C ONSTANT C ARRIER OR S WITCHED M ODE
Jumper W2 is used to select Constant Carrier or Switched Mode. This option
determines the use of the Request To Send signal, with selection dependent on
your particular application. When the jumper block is in the Constant Carrier
position, Constant Carrier Mode is selected. If Switched Mode is desired, the
jumper block would be placed in one of the four RTS/CTS delay positions. See
Figure 4-1 for the jumper’s location on the printed circuit board. Each mode is
discussed below.
In Constant Carrier Mode, the unit functions as if RTS is constantly asserted. The
EIA 485 transmitter is always on, and the unit CTS signal remains high. Any data
sent by the attached RS-232 device is automatically transmitted by the Line Driver.
The RTS LED on the unit’s front panel will always be on, and the CD indicator of
the remote Line Driver(s) will remain lit. Constant Carrier Mode is most
commonly used in multipoint applications that have a “master” device
communicating with two or more “slaves.” The master DTE is configured for
Constant Carrier Mode, while the slave devices are set to Switched Mode.

18
LD485S-MP
NOTE
Constant Carrier Mode pertains to full duplex or simplex operation only.
Half duplex does not apply since the RTS signal is constantly held high
in this mode, preventing any other signals from being raised in the
sequential fashion required by half duplex operation.
In Switched Mode, the Line Driver’s transmitter isn’t activated until the DTE
device asserts RTS. (Unlike Constant Carrier Mode, RTS is not held in a pseudo-
asserted state.) When the attached DTE device raises RTS, the Line Driver’s RTS
LED will light. The remote unit’s CD LED will light, indicating that a transmission
link has been established. Once the device drops RTS, the RTS and remote CD
lights will go out.
Table 3-3 provides a general guide to selecting Constant Carrier or Switched Mode
according to your specific operation (half or full duplex; point-to-point or
multipoint).
Table 3-3. Guide for Selecting Constant Carrier or Switched Mode
Operating Mode Constant Carrier or Switched Mode
2-Wire/Point-to-Point Both Line Drivers in Switched Mode
4-Wire/Point-to-Point User’s option for both units (normally both units configured
for Switched Mode)
2-Wire/Multipoint All units in Switched Mode
4-Wire/Multipoint All nodes in Switched Mode. Master unit is user’s option
(normally Constant Carrier Mode)
3.2.2 RTS/CTS D ELAY
If desired, the user can have a delay inserted after the RS-232 device raises RTS. It
will delay the return of CTS from the Line Driver to the DTE. This feature is useful
in applications that require time for the remote driver’s Carrier Detect (CD) signal
to activate the link between both RS-232 devices before CTS is raised. If CD hasn’t
been asserted before CTS, the link is considered inactive and data transmission
should not be attempted by the attached DTE.
In half duplex operation, the RTS/CTS delay is useful because it allows time to
establish which Line Driver will have control of the line to transmit data.
NOTE
RTS/CTS delay applies to Switched Mode only.

19
CHAPTER 3: Configuration
RTS/CTS Delay Options (Jumper W2)
• Constant carrier
• 0 msec (no delay)
• 11-msec delay (factory setting)
• 50-msec delay
• 160-msec delay
3.2.3 F ULL OR H ALF -D UPLEX O PERATION
Figure 3-2 shows the location of Jumper W3. This jumper allows you to select 2- or
4-wire operation. The factory setting is full duplex.
3.2.4 T YING S IGNAL G ROUND TO F RAME G ROUND
Jumper W1 provides the option of tying signal ground to frame ground. The
position is left open at the factory. If signal ground is to be connected to frame
ground, it is recommended that a 100-ohm 1⁄2-watt resistor be soldered in location
W1. A hardwire jumper may also be used; however, a measurement showing
minimal difference between signal and frame ground should be made to ensure
that ground circulating currents are limited to acceptable levels.