Modbus Communications; Electrical Connections; Host Computer Serial Communications - ABB ControlMaster CM10 Communications Supplement

ControlMaster CM10, CM15, CM30 and CM50
Universal process controllers and indicators,

5 MODBUS Communications

5.1 Electrical Connections

This section describes the connection of serial data cables between the master (host computer) and slave instrument on a
MODBUS serial link.

5.2 Host Computer Serial Communications

The serial interface option module operates using the MODBUS Remote Terminal Unit (RTU) Master / Slave protocol. An
appropriate RS422 / 485 communications driver must fitted to the host (master) computer. It is strongly recommended that the
interface has galvanic isolation to protect the computer from lightning damage and to increase signal immunity to noise pick-up.
Note. The MODBUS option provides the following facilities:

Standard RS422/485 communications.

MODBUS RTU protocol – the instrument is designed to operate as a Remote Terminal Unit (RTU) slave when
communicating with a master (host) system.

500V DC isolation from external connections to the instrument.

Two- or four-wire communication (selected at the MODBUS / Mode parameter) – see page 9.

1200, 2400, 4800, 9600, 19200, 38400, or 115200 baud transmission rate – see page 9.

Parity-checking (odd, even or none) – see page 9.
IM/CM/C–EN
1 1 1
/ , / and / DIN
8 4 2
5 MODBUS Communications
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