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Through the Modbus adapter it is possible to:
– Read measurements and logged values
– Read and write parameters settings of the controller
– Activate output relays
– Read status information
– Read device identification and type numbers
2.3. Compatibility
The Modbus adapter is compatible with any Power Factor Controller RVT Touchscreen. Other ABB controllers may be
connected with the adapter.
CAUTION: Be careful that the RS485 MODBUS ADAPTER is the one with a GREEN text color (3.3V power supply).
The one with a WHITE text color is reserved for the old model (5V power supply).
The Modbus protocol is compatible with all master stations that support the Modicon-defined Modbus serial communi-
cation protocol.
3. Serial interface considerations
The Modbus protocol communicates with the instrumentation by means of an industry standard serial interface. This
interface may be RS-232, RS-422 or RS-485. Some systems may also support the protocol over other busses or net-
works, such as Ethernet.
An RS-232 interface allows only two devices to be connected together.
RS-422 supports 1 driver and up to 10 receivers on a single network.
For bi-directional communications, special tri-state circuitry is provided. RS-485 supports up to 32 driver/receiver
pairs. With special hardware, the RS-422 and RS-485 limits can be expanded to allow as many as 248 devices on a
single network. Each device on a network must have a unique address, which may be soft configured. Address zero is
reserved for broadcast messages from the host to all slaves.
All devices on a network must also be configured with the same parameters, such as baud rate and parity. In design-
ing the communication architecture, one should consider communications performance when deciding how many de-
vices to connect to a host port. Generally, nearly twice the performance can be achieved by splitting the devices from
one port, onto two ports.
3.1. Communication mode
MODBUS protocol uses half-duplex communications, regardless of the hardware.
Half-duplex hardware shares the same lines for transmit and receive, whereas, full-duplex hardware has dedicated
transmit and receive lines.
STATUS
Approved
SECURITY LEVEL
Public
DOCUMENT ID
9AKK107045A9895
RS 48 5 A DAPTE R
REV.
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