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Modbus Communication and Connectivity

Figure 6 Exceeding maximum specifications

The maximum specification may be exceeded if measures are taken to

drive or boost the EIA-485 communication line. Two wire EIA485

repeaters are available through the Liebert Corporation. SiteScan’s

“REPOPT” will work sufficiently for this application. Consult the

SiteScan price book for pricing schedule and alternative solutions.

5.4 Modbus Slave Functions

5.4.1 Data Type

The OpenComms NIC-485 supports data in a register block as one of

the following types: Signed integer (16 bit) / Unsigned integer (16 bit) /

Signed long (32 bit); IEEE floating-point (32 bit); Null terminated

String.

A datum should consist of one or multiple registers. The leftmost byte

contains the MSB and the rightmost byte contains the LSB.

Modbus RTU Master

EIA-485 9600,N,8,1

Maximum of 32

devices with combined

cable length of 4000

feet

Modbus RTU Master

EIA-485 9600,N,8,1

Maximum of 32

devices with combined

cable length of 4000

feet

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Emerson MONITORING OpenComms Manuale Utente Pagina 20