Black Box LD485A-HS User manual

CUSTOMER
SUPPORT
INFORMATION
Order toll-free in the U.S. 24 hours, 7 A.M. Monday to midnight Friday: 877-877-BBOX
FREE technical support, 24 hours a day, 7 days a week: Call 724-746-5500 or fax [phone]
Mail order: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • E-mail: [email protected]
SEPTEMBER 1999
ME837A-R2 ME837AE
ME837C-R2 ME838A-R2
ME838AE ME838C-R2
BC00702 FA520A-R2
LD485A-HS
LD485A-HS Card
LD485A-HS Opto-Isolated
LD485A-HS Isolated Card
LD485A-HS OPTO-ISOLATED
TX RX CD RTS PWR
NORMAL
DLB
RX TX RTS CD
DCE
DTE
LD485A-HS
TX RX CD RTS PWR
NORMAL
DLB
RX TX RTS CD
DCE
DTE

FCC AND IC STATEMENTS
FEDERAL COMMUNICATIONS COMMISSION
AND
INDUSTRY CANADA
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.

LD485A-HS and LD485A-HS Opto-Isolated
Contents
Chapter Page
1. Specifications...................................................................................................1
2. Introduction ....................................................................................................3
3. Installation.......................................................................................................4
3.1 Jumper and Switch Configuration.........................................................4
3.1.1 DTE/DCE Configuration..........................................................4
3.1.2 Frame Ground/Signal Ground ................................................4
3.1.3 Half/Full-Duplex Operation.....................................................5
3.1.4 CTS Delay...................................................................................7
3.1.5 RS-485 Driver Enable.................................................................7
3.1.6 Half-Duplex Turnaround Delay ...............................................8
3.1.7 RS-485 Interface Terminated or Unterminated ......................8
3.1.8 Normal/Loopback Operation ..................................................9
3.1.9 RS-485 Interface Line Biased (Fail-Safe)..................................9
3.2 DCE Configuration/DTE Configuration............................................10
3.3 Typical Applications .............................................................................18
Appendix A: Pinning ........................................................................................25

1
CHAPTER 1: Specifications
Optical Isolation: ME838A-R2, ME838AE, ME838C-R2 only
Interface — (1) asynchronous RS-232 port (DTE/DCE selectable);
(1) asynchronous RS-485 port with improved surge protection and
switch-selectable line termination or line bias
Connectors — (1) DB25, female—RS-232 port;
(1) four-wire terminal block (TB1)—RS-485 port
Pins Supported — RS-232 port: TD, RD, RTS, CTS, CD, DTR, DSR, SG,
and FG; RS-485 port: TXA, TXB, RXA, RXB
Data Rate — 0 to 115 Kbps, transparent to data
Indicators — (5) LEDs: TX, RX, RTS, CD, and PWR
Temperature
Operating — 32 to 122° F (0 to 50° C)
Storage — -4 to 158° F (-20 to 70° C)
Humidity — 0 to 95% relative humidity, noncondensing
MTBF — Approximately 180,000 hours (ground benign environment)
Power — PS154 (for use with ME837A-R2, ME838A-R2): Input—120V, 60 Hz,
20W; Output—AC 17VCT, 0.7A; PS154E (for use with ME837AE, ME838AE):
Input—230V, 50 Hz, 20W; Output—AC 17VCT, 750 mA
Size — Standalone Unit: 1.8"H x 5.5"W x 8.5"D (4.6 x 14 x 21.6 cm)
Rackmount Card: 7.4"L x 4.7"W (18.8 x 11.9 cm); 0.6 inches thick (1.6 cm)
Weight — Standalone Unit: 1 lb. (0.5 kg);
Power supply only: PS154—0.4 lb. (0.2 kg), PS154E—1.1 lb. (0.5 kg)
1. Specifications

2
LD485A-HS and LD485A-HS Opto-Isolated
Operation — Point to Point or Multipoint
Half or Full Duplex
Transparent to data
Selectable RTS-to-CTS delay with option to
inhibit CTS if CD is present (DCE)
DTE or DCE configurable RS-232 port
Normal or loopback operation
Timeout Delay — 0.15, 0.7, 2, 7, or 70 msec (for the RS-485 driver enabled by
data feature)
Typical Speed Versus Distance — (4-wire point-to-point 26-AWG twisted pair)
SPEED DISTANCE
1200 bps 4 miles (6.4 km)
2400 bps 3 miles (4.8 km)
4800 bps 2.3 miles (3.7 km)
9600 bps 1.7 miles (2.7 km)
19,200 bps 1.2 miles (1.9 km)
38,400 bps 0.9 mile (1.4 km)
64,000 bps 0.75 mile (1.2 km)
115 Kbps 0.4 mile (0.6 km)
NOTE: Speed and distances will depend on
actual operating conditions.

3
CHAPTER 2: Introduction
The LD485A-HS is an RS-232-to-RS-485 interface converter that operates in
the same manner as a modem. It allows an RS-232 device to transmit data over
much longer distances than is normally possible (up to 4 miles—6.4 km—at
1200 bps). The advantage of the LD485A-HS over other line drivers and
modems is that it can also operate in multipoint applications. Depending on
the operating environment, as many as 64 devices can be linked together
using twisted-pair cable.
The opto-isolating models (ME838A-R2, ME838AE, ME838C-R2) protect one
segment of your extended network from problems that arise on the other.
Inside the RS-232↔485/422 Opto-Isolator/Converter, optical isolation
circuitry converts electrical signals to light and back again, to keep signal
noise and ground loops from crossing between segments of your RS-485
installation. That means the electrical noise from your factory floor won’t
affect your office communications, and the difference in ground potential
between buildings won’t damage your sensitive equipment.
Additional features include a manual loopback test to check the system wiring
for both the RS-232 and RS-485 interfaces, and transient protection on the
RS-485 interface to help prevent damage due to voltage transients on the
data line.
Although designed specifically to connect to other LD485A-HS line drivers,
the RS-485 port may be connected to any device with an RS-422 or RS-485
interface. For example, this would be useful in an industrial application where
RS-485 and RS-422 devices would be connected to the same LD485A-HS.
The LD485A-HS is available in standalone and rackmount versions. The
rackmount cards (part numbers ME837C-R2 and ME838C-R2) are designed
to be installed in the multi-function rack (part number RM005).
A 6-ft. DB25 male/DB25 female extension cable and a serial AT adapter
(DB9 female/DB25 male) are included with the ME837A-R2, ME837C-R2,
ME838A-R2, and ME838C-R2.
2. Introduction

4
LD485A-HS and LD485A-HS Opto-Isolated
This section describes the jumper and switch functions for configuring the
LD485A-HS. See Figure 1 (page 6) for the component locations.
To install your LD485A-HS:
1. Set each of the ten jumpers/switches for your application.
2. Connect the LD485A-HS devices together as shown in Figures 5
through 8 (pages 19–22).
3. Apply power. (PS154 or PS154E, depending on which LD485A-HS you
have. See Chapter 1 for more information.)
3.1 Jumper and Switch Configuration
NOTE
As you read this section, refer to Tables 1 and 2. Table 1 (page 11) lists
DCE jumper settings, and Table 2 (page 16) lists DTE jumper settings.
3.1.1 DTE/DCE C ONFIGURATION
A DIP shunt is used to select DTE or DCE configuration. For the
LD485A-HS to appear as a DTE device, put the DIP shunt jumper in socket
XW1B. For the LD485A-HS to appear as a DCE device, put the DIP shunt
jumper in socket XW1A.
3. Installation

5
CHAPTER 3: Installation
3.1.2 F RAME G ROUND /S IGNAL G ROUND
Jumper W7 ties signal ground to frame ground. The position is left open at
the factory. If signal ground is to be connected to frame ground, solder a
100-ohm, 1/2-watt resistor in location W7. A wire jumper may also be used.
Care must be taken to ensure that ground circulating currents are limited
to acceptable levels.
3.1.3 H ALF /F ULL -D UPLEX O PERATION
Jumper W8 selects half-duplex or full-duplex operation. Set W8 to the HALF
position for half-duplex operation. Set W8 to the FULL position for full-
duplex operation.
NOTE
When the jumper W9 is in the ON position and jumper W15 is in the A-B
position, the RS-485 driver is always turned on to enable transmission of
data. Therefore, half-duplex transmission cannot be performed. See
Section 3.1.5 for an explanation of the RS-485 driver.

6
LD485A-HS and LD485A-HS Opto-Isolated
Figure 1. Layout of the Printed Circuit Board.
K K
K K K
DS5 RX
DS2
CD/RTS
DS1
RTS/CD
DSR4
TX
DS3
PWR
DELAY
D - 5ms E - 35ms
S1
W17
W17 DRIVER ENABLE HOLD A - 70ms B - 7ms C - 2ms D - 0.7ms
E - 0.15ms
BC
A
W19
BC
A
W15 A-B = RTS/CD ENABLED B-C = DATA ENABLED
W9 30 mesc
10 mesc
0 mesc
ON
A-B RTS/CTS B-C RTS/CTS/CD
W5A
B C
W15
W8
ABC
ABCDE A
BCDE
AW16
W8 A-B = 2 WIRE B-C = 4 WIRE W16 TURNAROUND
A = 0ms B = 0.1ms C = 1ms
R49/W7
1 2 3 4
P2
O N O N
BIASTERM
XW1A DCE
TB1
XW1B DTE
W18
ABC
J1
TATBRARB

7
CHAPTER 3: Installation
3.1.4 CTS D ELAY
When the transmitter of a device is first turned on, an unstable carrier signal
is transmitted for several milliseconds. If data was sent during this period, it
would be received as distorted information. Setting a CTS delay on the
LD485A-HS allows the communications link to settle down before data can be
sent.
LD485A-HS as DCE
When the LD485A-HS is configured as a DCE device (DIP shunt in position
XW1A), jumper W9 controls the amount of delay from the time RTS (jumper
W5 in the A-B position) is received true until CTS is asserted true. If W5 is in
the B-C position, CTS will be inhibited if an RS-485 carrier is present when
RTS is raised. To select a CTS delay period, set jumper W9 to the 0-, 10-, or
30-msec position. Regardless of the delay setting selected, when RTS goes
false, CTS will immediately go false. If jumper W9 is in the “ON” position,
CTS will follow RTS.
LD485A-HS as DTE
When the LD485A-HS is configured as a DTE device (DIP shunt in position
XW1B), CTS is not supported.
3.1.5 RS-485 D RIVER E NABLE
The LD485A-HS’s RS-485 driver can be set to be enabled one of three ways: by
RS-232 control signals, by data, or constantly on.
Driver Enabled by RS-232 Control Leads
If your equipment raises CD or RTS, you can set the RS-485 driver to be
enabled by one of these leads. If your equipment does not have the capability
to raise CD or RTS, you will need to set the RS-485 driver to be enabled by
data or constantly enabled.
In order for an RS-232 control lead to enable the RS-485 driver, W15 must be
in position A-B and W9 must be set for 0, 10, or 30 ms.
• When the RS-232 port is selected as DTE (DIP shunt in the XW1B
position), the RS-485 driver will be enabled when CD (pin 8 of the
RS-232 connector) goes true.
• When the RS-232 port is selected as DCE (DIP shunt in the XW1A
position), RTS enables the driver.