Black Box Modem Fiber Optic Modem User Manual

MED100A 304 pg. 1 / 4  
6132-r1  
Model MED100A  
Fiber Optic Modem Sends  
RS-232, 422, 485 Signals Up to 2.5 Miles CE  
Description  
The MED100A 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 MED100A can replace converters and isolators when connecting remote devices, while providing the EMI/RFI and  
transient immunity of optical fiber.  
The MED100A supports both the Transmit and Receive data lines, and provides full hardware control of the RS-422/485  
driver with 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 multimode 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 MED100A 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 and 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  
receiver of the MED100A must be connected together by tying terminal blocks (L) and (H) together and (G) and (K)  
together. This allows the MED100A to communicate half-duplex over the same pair. Refer to Figure 1 for connection  
diagrams to your RS-422 or RS-485 equipment.  
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. The off-state bias resistor values can also be changed by removing R8 and R16 and replacing them with  
through-hole components.  
Figure 1: RS-422/485 Connection Diagrams  
MED100A  
MED100A  
422/485 4W Device  
485 2 Wire Device  
(K) RD A  
(K) RD A  
TD A (-)  
Data A (-)  
TD B (+)  
RD A (-)  
(L) RD B  
(G) TD A  
(L) RD B  
(G) TD A  
RD B (+)  
GND  
Data B (+)  
GND  
(H) TD B  
(M)  
(H) TD B  
(M)  
Black Box Corporation - 1000 Park Drive - Lawrence, PA 15055-1018  
Tech Support and Ordering: 724-746-5500 - Fax: 724-746-0746  
To contact us about Black Box products or services: [email protected]  
 
MED100A 304 pg. 3 / 4  
6132-r1  
Position 6 of SW1 sets the unit in a “Multidrop” mode or a “Point-to-Point” mode. When the MED100A is set in a  
“Multidrop” mode, data arriving on the Fiber Optic receiver is repeated back out the transmitter. When set in a “Point-to-  
Point” mode, data arriving at the Fiber optic receiver is not sent back out the Fiber Optic transmitter. Position 6 must be  
turned “On” when the MED100A is to be used in a multi-drop ring configuration. It must be turned “Off” when the  
MED100A is to be used as either end of a point-to-point communication line. See Figure 3 for typical system setups using  
the MED100A in its different modes.  
Table 2: 422/485 Switch Settings  
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 MED100A.  
Position 7  
TX Enable  
Position 8  
RX Enable  
RS-485  
ON  
ON  
2-Wire Mode  
(half duplex)  
RS-485  
ON  
OFF  
OFF  
4-Wire Mode  
(full duplex)  
RS-422 Mode  
(full duplex)  
OFF  
Table 2 illustrates the switch settings for typical setups.  
Multi-drop Operation  
A multi-drop configuration is created by forming a ring of MED100As. 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.  
Specifications/Features  
Transmission Line:  
Point-to-Point Transmission:  
Multi-Drop Transmission:  
Interfaces:  
Dual multimode optical cable  
Asynchronous, half or full-duplex  
Asynchronous, half duplex fiber ring  
RS-232, RS-422, or RS-485  
Connectors:  
DB25 female for serial connection, ST connectors for fiber  
4.3 x 2.3 x 0.95 in (11 x 5.9 x 2.5 cm)  
Terminal blocks  
Dimensions:  
Power Supply Connections:  
Recommended Power Supply:  
Temperature Rating:  
# PSD100 (12VDC, Input voltage range: 10-30 VDC)  
-40 to +80°C (-40 to +176°F)  
All specifications given using 62.5/125µm glass multi-mode fiber.  
Table 3: Recommended Maximum  
MED100 in a Fiber Ring Topology  
Baud Rate  
RS-232  
Operation  
RS-422/485  
Operation  
460.8 kbps  
230.4 kbps  
115.2 kbps  
57.6 kbps  
38.4 kbps  
19.2 kbps  
and lower  
N/A  
N/A  
2
2
4
Model Number:  
Description:  
Type:  
MED100A  
DIN mount Fiber Optic Converter  
Light industrial ITE equipment  
8
Application of Council Directive: 89/336/EEC  
8
16  
24  
Standards:  
EN 55022  
EN 61000-6-1  
EN 61000 (-4-2, -4-3, -4-4, -4-5, -4-6, -4-8, -4-11)  
16  
32  
32  
Black Box Corporation - 1000 Park Drive - Lawrence, PA 15055-1018  
Tech Support and Ordering: 724-746-5500 - Fax: 724-746-0746  
To contact us about Black Box products or services: [email protected]  
 
MED100A 304 pg. 4 / 4  
6132-r1  
Table 4: Operating Parameters  
Parameter  
Min.  
Typical Max.  
115.2 kbps  
Conditions  
Data Rates (RS-232 Operation)  
Data Rates (RS-422/485 Operation)  
Power Supply Voltage  
0 bps  
0 bps  
500 kbps  
30 VDC  
140 mA  
10 VDC 12 VDC  
Power Supply Current Draw  
Optic Wavelength  
Full RS-485 Termination  
820 nm  
Fiber TX Launch Power  
Minimum Required Fiber Rx Power  
Maximum Receiver Power  
Coupled Power Budget  
Fiber Range  
-17 dBm -13 dBm -10 dBm  
-25.4 dBm -24 dBm  
-10 dBm  
12.1 dB  
2.5 miles  
End to End Delay  
2000 ns  
550 ns  
900 ns  
50 ns  
2650 ns  
1000 ns  
1100 ns  
120 ns  
Point-to-Point RS-232 Operation (See Notes 1 & 2)  
Point-to-Point RS-422/485 Operation (See Notes 1 & 2)  
Point-to-Point RS-232 Operation (See Note 3)  
Point-to-Point RS-422/485 Operation (See Note 3)  
(See Note 1)  
End to End Delay  
End to End Skew  
End to End Skew  
Maximum Total Fiber Ring Length  
Delay between Rx & Tx on a fiber ring 52 µs  
5 Miles  
(See Note 4)  
Note 1: For the total transmission time over long fibers, the time to transverse the fiber must be considered if delay is an issue. Light takes about 8.05 microseconds to travel over 1 mile of fiber.  
Note 2: When operating in a ring configuration, each node in addition to the two in the point-to-point specification adds an additional 100 to 200 nanoseconds of delay.  
Note 3: When operating in a ring configuration, each node in addition to the two in the point-to-point specification adds an additional 50 to 70 nanoseconds of skew.  
Note 4: When operating in a ring configuration, each serial device must wait at least this minimum time between receiving data from the ring and transmitting back on to it.  
Figure 4: MED100A Circuit Diagram  
Black Box Corporation - 1000 Park Drive - Lawrence, PA 15055-1018  
Tech Support and Ordering: 724-746-5500 - Fax: 724-746-0746  
To contact us about Black Box products or services: [email protected]  
 

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