Flowserve DDC-100 Modbus Direct-to-Host User Manual download pdf (Page 5)

4 DDC-100 Direct-to-Host Programming Guide FCD LMAIM4019-00 FCD LMAIM4019-00 DDC-100 Direct-to-Host Programming Guide 5

• Provides a safe and reliable communications path between the supervisory control system and

valve actuator network. This eliminates an unnecessary single point of failure that would exist if

the valve control network required a gateway device.

• Enhances the operational relationship between the customer and the customer’s preferred system

integrator.

2.2 Deliverables for Successful

Direct-to-Host Implementations

Each Direct-to-Host installation requires coordination to ensure that every supplier understands

their deliverable responsibilities. When suppliers understand particular obligations and perform

the tasks in an orderly and timely fashion, the DDC-100 Network installation process will progress

very smoothly. Appendix A outlines a “typical” chart detailing areas of responsibility or supplier

deliverables for installing a DDC-100 system. This appendix is a guideline and may vary from

project to project.

Field Unit

Monitoring and

Control

Flowserve Limitorque valve actuators that are DDC-100 Network compatible can be controlled and

monitored by sending queries and receiving responses over a serial data network. The DDC-100

Network uses the non-proprietary Modbus message protocol and EIA RS-485 standard for the

physical communication link.

Table 3.1 – Field Unit Communication Parameters

Parameter Options Default

Message Framing RTU, ASCII RTU

Baud Rate 1200, 2400, 4800, 9600, 19,200 9600

Data Bits 8 8

Stop Bits 1 1

Parity None None

Error Checking CRC-16 (RTU), LRC (ASCII) CRC-16 (RTU)

Field Unit Address Range 1–250 Conﬁgurable Conﬁgurable

3.1 Use of Coils and Registers

for Monitoring and Control

The material in this section is a brief tutorial and general discussion of the use of Modbus queries

and responses to control valve actuators. The detailed discussion of the commands will be given in

Section 3.2.

The Modbus communications protocol allows for working with two types of information—coils

(or bits) and registers (or 16-bit words). Coils are either ON (1) or OFF (0) and are used in direct

relation to relays (that have coils). For example, in a typical actuator, Coil 1 is energized to CLOSE

the actuator and Coil 2 is energized to OPEN the actuator. Register information is used for control

functions that do not involve coils. An example would be to write a command value to energize the

open or close coil or move the actuator to a position of 0 to 100% of open.

1 2 3 4 5 6 7 8 9 10 ... 32 33

No comments

Flowserve DDC-100 Modbus Direct-to-Host User Manual Page 5