B&B Electronics FOSTCDR User Manual

DIN Mount Fiber Optic Converter CECE

Model FOSTCDR

Document No. FOSTCDR2999

This product Designed and Manufactured

In Ottawa, Illinois USA

of domestic and imported parts by

B&B Electronics Mfg. Co. Inc.

707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350 USA

Phone [phone] -- General Fax [phone]

Home Page: www.bb-elec.com

Sales e-mail: [e-mail] -- Fax [phone]

Technical Support e-mail: [e-mail] -- Fax [phone]

© Copyright 1999 B&B Electronics -- August 1999

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B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

Table of Contents

DESCRIPTION.................................................................................................1

RS-232 CONNECTIONS ...............................................................................1

RS-422 & RS-485 CONNECTIONS............................................................1

FIBER OPTIC CONNECTIONS ...................................................................2

DIP-SWITCH SETUP......................................................................................3

MULTI-DROP OPERATION.........................................................................5

SPECIFICATIONS ..........................................................................................6

FOSTCDR DIAGRAM....................................................................................7

FOSTCDR2999 Manual Table of Contents i

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

Description

The FOSTCDR is designed to provide the most versatile
connection possible between any asynchronous serial equipment
using Fiber Optic cable. It allows any two pieces of asynchronous
serial equipment to communicate full or half-duplex over two fibers at
typical distances up to 2.5 miles. The converter can also be set up in
"Repeater" mode to create a multi-drop master/slave configuration,
allowing one serial device to talk to multiple slave devices around a
fiber ring. The DIN rail mountable box makes it ideal for industrial
cabinets and enclosures.

RS-232 data signals up to 115.2K bps and RS-422, or RS-485
data signals up to 460K bps are supported. Different standards can
be mixed and matched to allow RS-232 devices to connect to your
RS-422 or RS-485 system. This means the FOSTCDR can replace
converters and isolators when connecting remote devices, while
providing the EMI/RFI and transient immunity of optical fiber.

The FOSTCDR supports both the Transmit and Receive data
lines, and provides full hardware control of the RS-422/485 driver with
B&B's Automatic Send Data Control circuit. Timeouts are dip-switch
selectable between 0.10 and 2.2 ms. All serial connections are
provided on terminal blocks, while the multi-mode fiber is connected
via two ST connectors. The unit is powered by 10 to 30VDC at 140
mA max.

RS-232 Connections

Connection of the FOSTCDR is simple and straightforward. The
RS-232 driver and receiver are connected to 2 terminal blocks. The
RS-232 DATA OUT is on terminal block (A), and the RS-232 DATA IN
is on terminal block (D). Ground is located on terminal block (B) and
(C), and power comes in on terminal block (F).

RS-422 & RS-485 Connections

The RS-422/485 driver and receiver are connected to 4 terminal
blocks. Signal ground is on terminal block (M), and power comes in
on terminal block (J). When connecting to a four-wire RS-422/485
device or system, connect the output of your device to terminal block
(L) (RDB or RD+) and terminal block (K) (RDA or RD+). Connect the
input to your device to terminal block (H) (TDB or TD+) and terminal
block (G) (TDA or TD-). For two-wire RS-485 systems, the driver and

FOSTCDR2999 Manual 1

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

receiver of the FOSTCDR must be connected together by tying
terminal blocks (L) and (H) together and (G) and (K) together. This
allows the FOSTCDR to communicate half-duplex over the same pair.
Refer to Figure 1 for connection diagrams to your RS-422 or RS-485
equipment.

Figure 1: RS-422/485 Connection Diagrams

422/485 4W Device

FOSTCDR

485 2 Wire Device

FOSTCDR

TD A (-)
TD B (+) (L) RD B

RD B (+)

(K) RD A

(G) TD ARD A (-)

(H) TD B

(M)GND

Data A (-)

Data B (+)

(K) RD A

(L) RD B
(G) TD A

(H) TD B

(M)GND

If termination is needed, the PCBD is laid out to allow a
termination resistor (Rt) to be soldered in across the RD(A) and
RD(B) lines. Removing R8 and R16 and replacing them with through­hole components can also change the off-state bias resistor values.
Before making modifications to the FOSTCDR, be sure to consult
B&B Electronics’ free RS-422/485 Application Note or other sources
of information to see if termination is necessary. The Application
Note is available from our Web site, or call and we will happily send
you one at no charge.

Fiber Optic Connections

The FOSTCDR uses a separate LED emitter and photo-detector
operating at 820 nm wavelength. Connections to the emitter and
detector are on ST type connectors. Most multi-mode glass fiber
size can be used including 50/125 µm, 62.5/125 µm, 100/140 µm,
and 200 µm. One fiber is required for each connection between a
transmitter and receiver. In a point to point configuration, two fibers
are required between the two modems, one for data in each direction.
A multi-drop ring configuration requires one fiber between TX and RX
around the loop. See Figure 2 for typical point to point and multi-drop
configurations.

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The most important consideration in planning the fiber optic link is
the “power budget” of the fiber modem. This value represents the
amount of loss in dB that can be present in the link between the two
modems before the units fail to perform properly. This value includes
line attenuation as well as connector loss. For the FOSTCDR the
typical connector to connector power budget is 12.1 dB. Because

62.5/125 µm cable typically has a line attenuation of 3 dB per Km at
820 nm, the 12.1 dB power budget translates into 2.5 miles. This
assumes no extra connectors or splices in the link. Each extra
connection would typically add 0.5 dB of loss, reducing the possible
distance by 166 m (547 ft.). The actual loss should be measured
before assuming distances.

Figure 2: Typical Setups

Point to Point

RS-232
RS-422

or RS-485

Device

or System

Full Duplex

RS-232
RS-422

or RS-485

Device

or System

FOSTCDR

SW1:6 = OFF SW1:6 = OFF

TX

RX

Duplex

Multimode

Fiber

RX

TX

Multi-Drop Ring

TX

FOSTCDR

SW1:6 = OFF

MASTER

Multimode

RX

Fiber

SLAVE

TX

SW1:6 = ON

FOSTCDR

RS-232
RS-422

or RS-485

Device

or System

RX

SLAVE

FOSTCDR

TX

SW1:6 = ON

FOSTCDR

RS-232
RS-422

or RS-485

Device

or System

RX

or RS-485
or System

SLAVE

RS-232
RS-422

Device

TX

SW1:6 = ON

FOSTCDR

RS-232
RS-422

or RS-485

Device

or System

Dip-Switch Setup

The Dip-Switch (SW1) on the FOSTCDR defines the mode of
operation when being used for RS-422 or RS-485. Positions 1
through 5 on the switch determine the timeout of the RS-485 driver.
Because the driver is controlled by hardware, a specific time must be
set to tell the hardware how long to wait for data on the fiber side
before turning off the RS-422/485 driver. If this time is set too short,

RX

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B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

Pos. 1

Pos. 2

Pos. 3

Pos. 4

Pos. 5

Time(ms)

Not Used

Not Used

Not Used

Not Used

Not Used

Not Used

Not Used

the driver could be disabled before transmission is complete, resulting
in data corruption. If the time is set too long, the RS-485 device may
respond before the RS-422/485 driver in the FOSTCDR is disabled,
corrupting this response. We recommend that the timeout be set for
approximately one character time or longer. The character times for
several different baud rates are selectable on switch positions 1
through 5. If you need a different timeout than what is provided, R10
can be removed and replaced with a different value R9. Table 1
shows the different timeout values for the switch positions as well as
some typical R9 replacement values.

Table 1: RS-485 Timeout Selection

Baud Rate

1200 ON OFF OFF OFF OFF 820 KΩ 8.20
2400 ON OFF OFF OFF OFF 430 KΩ 4.30
4800 OFF OFF OFF OFF ON
9600 OFF OFF OFF ON OFF

19.2K OFF OFF ON OFF OFF

38.4K OFF ON OFF OFF OFF

57.6K ON OFF OFF OFF OFF

76.8K ON OFF ON ON OFF

115.2K ON ON ON OFF OFF

153.6K ON OFF OFF OFF OFF 6.2 KΩ 0.06

230.4K ON OFF OFF OFF OFF 4.3 KΩ 0.04

460.8K ON OFF OFF OFF OFF 2.2 KΩ 0.02

R9

2.20

1.30

0.56

0.27

0.22

0.14

0.10

Position 6 of SW1 sets the unit as a “Repeating” module or a
“Terminating” module. When the FOSTCDR is set as a “Repeating”
module, data arriving on the Fiber Optic receiver is repeated back out
the transmitter. When set as a “Terminating” module, data arriving at
the Fiber optic receiver is not sent back out the Fiber Optic
transmitter. Position 6 must be turned “On” when the FOSTCDR is to
be used as one of the Slaves in a multi-drop ring configuration. It
must be turned “Off” when the FOSTCDR is to be used as the Master
in a multi-drop configuration or as either end of a point to point
communication line. See Figure 3 for typical system setups using
the FOSTCDR in its different modes.

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(full duplex)

Positions 7 and 8 of SW1 determine when the RS-422/485 driver
and receiver are enabled. Position 7 controls the driver and Position 8
controls the receiver. For RS-422 operation, set both switches to the
“Off” position. For multi-drop RS-485 four-wire systems, position 7
should be “On” and position 8 should be “Off.” This allows the
receiver to be enabled all of the time and eliminates some possible
timing problems. For RS-485 two-wire systems, both switches
should be in the “On” position. This disables the RS-422/485 receiver
whenever the driver is enabled, preventing data from being echoed
back to the fiber side of the FOSTCDR. Table 2 illustrates the switch
settings for typical setups.

Table 2: 422/485 Switch Settings

RS-485 2-Wire Mode

(half duplex)

RS-485 4-Wire Mode

(full duplex)

RS-422 Mode

Position 7

TX Enable

ON ON

ON OFF

OFF OFF

Position 8

RX Enable

Multi-Drop Operation

A multi-drop configuration can be created by forming a ring of
FOSTCDRs. Each transmitter is tied to the following converter’s
receiver, starting at a master node and continuing around to each
slave and back to the master. By setting SW1:6 to the “On” position
on the slaves, all data sent from the master or preceding slaves is
echoed back out the fiber transmitter to the rest of the slaves and
eventually back to the master node.

Because all data is echoed back, there are special
considerations when constructing a multi-drop system. The master
will see its own transmitted data. This means that the master device
must be full-duplex (RS-232, RS-422, or four-wire RS-485) and that it
must be capable of ignoring or otherwise accepting its own echoed
transmission. Slaves must also be able to accept data from previous
slaves in the loop.

FOSTCDR2999 Manual 5

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

Specifications

Transmission Line: Dual multi-mode optical cable
Point to Point Transmission: Asynchronous, half or full-duplex
Multi-Drop Transmission: Asynch., half duplex, master/slave, ring
Interfaces: RS-232, RS-422, or RS-485
Data Rates : 0 to 115.2K bps RS-232; 0 to 460K bps RS-422/485
Typical Range: Up to 2.5 miles (4.0 km) on multi-mode glass fiber
Coupled Power Budget: 12.1 dB
Optic Wavelength: 820 nm
Connectors: Terminal blocks/serial connection, ST connectors/fiber
Power Supply: Requires 10 – 30 VDC @ 140 mA max.
Temperature Range: -20°C to 80°C
Dimensions: 4.4”L x 3.0”W x 1.0”H (11.2 x 7.6 x 2.5 cm)

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B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

FOSTCDR Diagram

Figure 3: FOSTCDR Circuit Diagram

FOSTCDR2999 Manual 7

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]

FEDERAL COMMUNICATIONS COMMISSION
RADIO FREQUENCY INTERFACE STATEMENT

Class A Equipment

This equipment has been tested and found to comply with the
limits for Class A digital device, pursuant to Part 15 of the FCC
Rules. These limits are designed to provide reasonable protection
against harmful interference when the equipment is operated in a
commercial environment. This equipment generates, uses, and can
radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to
radio communications. Operation of this equipment in a residential
area is likely to cause harmful interference, in which case the user
will be required to correct the interference at personal expense.

FCC Class A Equipment Statement