Datasheet

Modbus TCP Communication HIMA H41q/H51q ↔

↔↔

↔ Emerson DeltaV

These blocks can be imported as needed via the bulk import feature of DeltaV and than be copied

together in one control module for import and one control module for export of binary data.

2.4. Validation of Modbus TCP Communication

The Modbus TCP communication between the H41q/H51q PES and the DeltaV DCS is supervised

through the VIM Modbus TCP Master. The status changes are alarmed in the operator interface as

controller status change after approximately ten seconds of inactivity.

For safety critical data transfer from DCS to PES like maintenance override switches a watchdog

signal should be used for supervision of the communication. When the watchdog does not change all

set maintenance override switches should be released. The watchdog should be implemented as a

ramped unsigned integer variable to avoid malfunction through under sampling which could occur with

binary signals.

The DeltaV Diagnostic Application and also the Mynah Diagnostic Application offer diagnostic support

for troubleshooting like signal status, online signal values and communication counter. For more

information about diagnostic support refer to [4] and [5].

Note 8:

When a Modbus TCP communication failure occurs the status of the simulated serial

cards in DeltaV Diagnosis change to “Bad” displayed with a yellow question mark.

After restoring communication it could be necessary to clear the fault using the “Clear

Saved Fault Information” option in the context menu of a simulated serial card in

DeltaV Diagnosis.

3. Summary

Modbus TCP communication between HIMA PES and the DeltaV DCS is an alternative to serial

Modbus RTU communication via RS-485 or Profibus DP communication. The advantages of the

described communication becomes effective for:

• Network layouts with several communication masters in one single network (due to multi

master capability)

• Network layouts with larger numbers of HIMA PES as communication slaves (due to the large

possible data volume of the VIMs)

• Larger data volumes to be transferred from one or several HIMA PES to a single DeltaV

controller (due to faster speed [2 – 3 times faster than Modbus RTU] and lower susceptibility

of communication cycle times to increasing data volumes)

• Network layouts where simplicity in connecting devices is preferred (due to the ability of

integrating all HIMA PES communication in one redundant ethernet)

For other applications where the above mentioned advantages do not apply Profibus DP (fast and

inexpensive but non-redundant and volume-limited) or Modbus RTU (inexpensive but slower and more

volume-limited) are still viable alternatives.