1.0 Description

The Point-to-Point Fiber Optic Communications Module provides for the remote connection of devices with asynchronous RS-232 (V24), RS-422 and RS-485 interfaces, using dual-fiber cable as the transmission medium.

These modules offer special features simplifying the link up of asynchronous serial equipment :

• Dual fiber optic cable connections provide total immunity from all electrical and electromagnetic disturbances.
• Interconnection of dissimilar asynchronous interface equipment e.g., RS-232, RS-422 or RS-485.
• Remote connections over fiber links greater than 3 Km up to 64 KBPS.

The Model 8242-X product range is available in plastic DIN rail mountable boxes. This same DIN mountable box can also be wall mounted with screws.

2.0 Principles of Operation

2 .1 Structure
All of the members of the 8242 family of fiber optic communication modules are structured as shown below:

2.2 Interface stage (I/O)
The interface stage provides the required interface circuits : RS-232, RS-422 or RS-485

2.3 Intermediate stage
This stage controls the operation of the communications protocol offered by the 8242, and in particular the Half-Duplex operation used in Multipoint mode for RS-422 and RS-485 interfaces.

Half-Duplex Control:
The lack of a control circuit on the RS-485 side requires that the Model 8242-3 to take control of managing the driver for transmitting data towards the RS485 line. The Model 8242-3 accomplishes this by detecting a start bit which then enables the transmitter (T0), and keeps it enabled until a half-bit following the last stop bit.

If a new start bit is detected during "T2" time, the driver is kept active until the next character and so on. The microprocessor controls the T0, T1 and T2 times in accordance with the transmission parameters indicated by the user via the S1 dip-switch block (Section 4-2)

2.4 Fiber optic stage
The fiber optic stage, common to the entire product range, assures compatibility between different models as well as the data transfer via fiber optic cabling of 50/125 or 62.5/125 microns.

2.5 Operating Modes
The Model 8242 features five modes of operation: Single-Master, Dual-Master, Point to Point, Broadcast and Link Extender.

2.5.1 Single-Master Mode
This mode is employed frequently for applications calling for a single master station and several secondary stations.


The Master station broadcasts to the secondary stations and the secondary station that is "addressed" transmits to the Master station.

- Broadcast sequence transmit by the Master station :


- Response sequence transmit by "addressed" B station :


2.2.2 Dual-Master Mode
This running mode provides an element of security for the Multipoint link-up. Here, a second Master station (Back-up station), can broadcast to the secondary stations when the "standard" master is not able to.

- Broadcast sequence transmit by Master station :


- Broadcast sequence transmit by the Back-up Master :


- Response sequence transmit by secondary station B "addressed" :


2.2.3 Point to Point Mode
This mode provides long distance, immunity free, data transmission for serial type interfaces RS-232, RS-422 and RS-485 via a fiber optic connection.


When linking two fiber optic modems be sure to take into account TD and RD polarity.

2.2.4 Broadcast Mode
This operating mode as the name indicates, allows the Model 8242 to be used as a Broadcast device between a Master station and Secondary stations via asynchronous FO modems over two FO lines. This function is particularly suitable when a campus type application will not permit the use of a single Multipoint bus for the control of peripheral devices.

2.2.4.1 Broadcast Mode
Example 1


2.2.4.2 Broadcast Mode
Example 2


2.2.4.3 Broadcast Mode
Example 3


2.2.5 Link Extender Mode
This mode will allow you to double the transmission distance between Model 8242 asynchronous modems over a fiber optic connection. A maximum transmission distance of up to 5 Kms at 3dBm is possible depending upon the quality of fiber used and the fiber connection.


3.0 Connection/Cabling

3.1 Interface Side
Each Model 8242 is equipped with a screw-terminal block connector for peripheral device connection.

Interface circuits are indicated to the right of the vertical mark ( O ) on the front panel of the Model 8241. A ( ) mark indicates the type of interface model.

• RS-232 : RS-232 interface (V.24)
  COM circuit corresponds to 0V (electrical standards)
  
• RS-422 / RS-485
  COM circuit depends upon the interface type and the configuration
  With the 2 wire RS-485 model, the RS-485 bus is available on the R+ (bus side +) and R- (bus side -)

NOTE : The GND circuit can also be connected to the power supply ground by strapping ST4.

3.2 Multipoint Fiber Optic Connection
Each Model 8242 has two fiber optic connections, labelled Upstream (UP) and Downstream (DOWN). Each is equipped with ST type connectors.


The Multipoint connection is made by daisy-chaining the TX/RX "UP" interface with that of the "DOWN".


The modems located at the two extremes of the link must not be in Multipoint mode configuration.
NOTE :
Depending upon the number of stations in the daisy chain, it may be necessary to provide "signal regeneration points" to overcome data signal distortion.
4.0 Configuration

- SELECTION OF OPTIONS :
The configuration of a piece of equipment consists of matching its characteristics to those of the unit or units to which it is connected.
This adaptation is made by the use of DIP-SWITCHES and HEADERS (JUMPERS)

- DIP-Switches :


These Dual Inline Package (DIP) switches have 4 or 8 contacts, with identification by a number, indicating the ON (Closed), side of the switch.

- Headers (Jumpers)
The location and use of Headers on a circuit board can sometimes cause difficulties. The following are the types used on the units.

Single Header : This is composed of a fixed base, with two upright posts soldered to the circuit board, and a separate header, which can be installed to link the two posts. Thus there are two possiblities, connection or non-connection between the two posts.


Double Header : The fixed part in this case has three posts, with a cut-out showing post 1. Thus there are a number of possible configurations, according to the position of the Header.


NOTE : Before changing the postions of DIP switches and/or Headers, it is strongly recommended:

• To check the Factory Configuration, which will allow you to locate the Headers more easily.
• To make a note of the changes to be made.
• To pay attention to the location of single and double Headers, particularly where there is a line of Headers together.

4.1 Peripheral Interface
Depending on the type of interface, a range of transmission parameters are available, which may be altered prior to installation.
Parameter selection is by plastic jumpers on the interchangeable interface module.

4.1.1 RS-232 Inteface (V24) Model 8242-1

The RS-232 interface is configured in DCE mode.
- Jumpers :

4.1.2 RS-422 Interface (Model 8242-2)
DIP Switch S1 : Transmission specifications:

- DIP Switch S2 : V11 I/O Configuration :

- Jumpers :

* High-speed mode requires S2-8 in OFF position

- Running Mode :

4.1.3 Interface RS-485 (Model 8242-3)
DIP Switch S1 : Transmission specifications:

- DIP Switch S2 : RS-485 I/O Configuration :

- Jumpers :

* High-speed mode requires S2-8 in OFF position

- Running Mode :

4.2 Factory Configuration

4.2.1 Model 8242-2, RS-422 (V11) and Model 8242-3, RS-485

NOTE : Factory settings = Point/Point, 4 wires.
The Series 8241 is supplied in a plastic DIN rail mountable box. This same DIN mountable box can also be wall mounted with screws.

5.0 Technical Description

The Series 8242 is supplied in a plastic DIN rail mountable box. This same DIN mountable box can also be wall mounted with screws.

5.1 Front Panel


- ON Indicator : Power ON.
- TD Indicator : Data transmitted from the Model 8242 interface.
- RD Indicator : Data received at the Model 8242 interface.

5.2 Pcb Layout
Power Supply Board : Soldered side

Power Supply Board : Component side


6.0 Specifications

Interface: RS-232(V24), RS-422(V11) or RS-485.

Transmission Mode: Serial, Asynchronous.

Running Mode:
Bidirectional HDX : RS-485 2-wire
FDX : RS-232(V24), RS-422(V11)RS-485 4-wire

Data Rate:
8242-1/2 : Up to 64 KBPS.
8242-3 : Up to 38.4 KBPS.

Fiber Optic Connection:
FDX, Dual fiber
Fiber optic cable 50/125 or 62.5/125 microns
Fiber Budget : 15 dBm.
Transmit Level : - 15 dBm.
Receive Level: - 30 dBm.
Wavelength : 850 nm.
Connectors : Type ST.

Fiber Transmission Distance: Depends on fiber attenuation per km.
Example : 4 Kms for an attenuation of 3 dBm/Km.

Dimensions: 75 x 100 x 125 mm(h x l x w)

Power: 110VAC/60Hz or 230V AC/50Hz (10VA), as ordered

Environment:
Operating temperature: 0° to 70° C
Storing temperature: -20° to 70°C
Humidity 10% to 90% No condensation.

7.0 Help

If any assistance is required call Bomara Associates at (800)-5BOMARA or (978)-452-2299.
Technical Support E-Mail: bobr@bomara.com
or use our Online Contact Form

Document No. 0315-0284
Rev. -

Warranty

Telebyte warrants the equipment to be free from defects in material and workmanship, under normal and proper use and in its unmodified condition, for 12 months, starting on the date it is delivered for use. TELEBYTE's sole obligation under this warranty shall be to furnish parts and labor for the repair or replacement of products found by TELEBYTE to be defective in material or workmanship during the warranty period. Warranty repairs will be performed at the point of manufacture. Equipment approved for return for warranty service shall be returned F.O.B. TELEBYTE factory and will be redelivered by TELEBYTE freight prepaid, except for non- continental U.S.A. locations. These deliveries will be sent COD freight and import/export charges.

THE ABOVE WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, STATUTORY OR OTHERWISE, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TELEBYTE SHALL NOT BE LIABLE FOR ANY DAMAGES SUSTAINED BY RESELLER OR ANY OTHER PARTY ARISING FROM OR RELATING TO ANY EQUIPMENT FAILURE, INCLUDING, BUT NOT LIMITED TO CONSEQUENTIAL DAMAGES NOR SHALL TELEBYTE HAVE ANY LIABILITY FOR DELAYS IN REPLACEMENT OR REPAIR OF EQUIPMENT.

Out of warranty equipment may be returned to the Greenlawn, NY customer service facility prepaid as described above. Return shipping charges will be billed to the customer. The repaired unit will have a 90 day warranty. In those cases where "NO TROUBLE" is found, a reduced charge will be billed to cover handling, testing and packaging.