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MED100A 304 pg. 1 / 4 6132-r1

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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

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

422/485 4W Device

TD A (-)

TD B (+) (L) RD B

(K) RD A

(H) TD B

(G) TD A

RD A (-)

RD B (+)

(M)GND

FOSTCDR

485 2 Wire Device

Data A (-)

(L) RD B

(K) RD A

(H) TD B

(G) TD A

Data B (+)

(M)GND

FOSTCDR

MED100A MED100A

Summary of content (4 pages)

PAGE 1
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.
PAGE 2
MED100A 304 pg. 2 / 4 6132-r1 Fiber Optic Connections The MED100A 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 multimode 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.
PAGE 3
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-toPoint” 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.
PAGE 4
MED100A 304 pg. 4 / 4 6132-r1 Table 4: Operating Parameters Parameter Data Rates (RS-232 Operation) Data Rates (RS-422/485 Operation) Power Supply Voltage Power Supply Current Draw Optic Wavelength Fiber TX Launch Power Minimum Required Fiber Rx Power Maximum Receiver Power Coupled Power Budget Fiber Range End to End Delay 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 Min. 0 bps 0 bps 10 VDC Typical 12 VDC Max. Conditions 115.