MA-49

What does this converter do?

It converts asynchronous serial communication between RS-232 and RS-422 or RS-485 interfaces, allowing equipment with different serial standards to exchange data.

Which communication modes can it handle?

The converter can operate in full-duplex, half-duplex or simplex configurations, depending on the interface wiring and switch settings.

What is the maximum data rate?

The maximum specified data rate is 100 kbit/s.

Can it be used with both RS-422 and RS-485 networks?

Yes. It can be configured for four-wire RS-422 communication or two-wire RS-485 communication.

What is the maximum transmission distance?

The RS-422/485 interface can reach up to 1,200 metres when suitable twisted-pair cable is used. The stated distance is based on cable with a 0.3 mm² conductor area and capacitance of approximately 42 pF per metre.

How many devices can be connected to the serial bus?

The documented network configuration allows up to 32 connections. The network should use a bus layout rather than a star layout.

Does it provide electrical isolation?

Yes. The MA-49 provides galvanic isolation through optocouplers for data transmission and a transformer for the power supply. Its specified isolation voltage is 1,500 V.

How is the RS-232 interface connected?

The RS-232 side uses a 25-position female D-sub connector configured as DCE. Signals include transmitted data, received data, RTS, CTS, DSR, DCD, DTR and signal ground.

How is the RS-422/485 interface connected?

The line interface uses a five-position detachable screw terminal. The terminals are assigned to receiver A', receiver B', transmitter A, transmitter B and cable shield.

What power supply arrangement is required?

The converter receives external ±20 V DC power through a PS-02 power supply installed in an RV-01 rack. One PS-02 can power a maximum of nine converter cards in the rack.

How is the unit mounted?

It is designed for installation in a Westermo RV-01 rack and occupies one card slot. The converter card measures 100 by 100 mm and weighs approximately 0.1 kg.

What environmental conditions are specified?

The specified ambient operating temperature is 5°C to 50°C. Permitted relative humidity is 0% to 95%, provided that condensation does not occur.

What do the front indicators show?

The indicators display RTS, CTS, DCD, received data and transmitted data activity, together with the presence of the positive and negative 12 V supply rails.

Can transmitter direction be controlled by serial status signals?

Yes. Switch settings allow the transmitter to be activated by RTS or DTR. These signals can control transmitter activity in multidrop four-wire systems and communication direction in two-wire RS-485 systems.

Does the converter include selectable line termination?

Yes. Its switch settings provide termination with fail-safe biasing for two-wire or four-wire communication, as well as an option for no termination. Termination should normally be applied at the ends of the network bus.

What cable type is recommended for the line connection?

Twisted-pair cable is recommended for RS-422/485 communication. Shielded cable is preferable in electrically noisy industrial environments, with the shield connected at one end to reduce unwanted ground currents.