Onicon System-30 MODBUS BTU Manual de usuario descargar pdf (Pagina 28)

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System-30 BTU Measurement System MODBUS RTU RS485 04/14 - 0583-1 / 18345 Page 28

4.7 MODBUS MEMORY MAP

ONICON Btu meters equipped with MODBUS RTU serial communications provide volume and

energy rate data, temperature data, totalized volume and totalized energy data in a variety of

engineering units. For example, supply and return temperatures are available in both degrees F

and degrees C. You select the engineering units you wish to use by mapping to the appropriate

registers.

4.7.1 MODBUS RTU Register Format and Networking Information

1. All registers are 16 bit MODBUS Holding Registers

2. MODBUS Holding Registers are used in 4 different ways.

A. As an analog value: In some cases these values are scaled

by multiplying the register contents by a xed multiplier.

B. As a status indicator where the register value can only

be “1” or “2”.

C. As a mode indicator where the value indicates current operating mode

such as; “1” = single, “2” = dual, or “3” = bi-directional.

D. As a control register where the host can write a value to reset total(s).

3. Registers 40001 through 40068 are unsigned integer registers (0 to 65,535) except

for 40024 and 40025. These are 16 bit signed integer values (-32,768 to +32,767).

Registers 41003 through 41064 are 32 bit single precision oating point values.

41001, 41002 and 41065 through 41069 are unsigned integer registers.

4. MODBUS function codes supported:

CODE DESCRIPTION

03 Read Holding Registers

06 Preset Single Registers

16 Preset Multiple Registers

17 Report Slave ID

5. Connection information: RS485, 2-wire (half duplex)

6. Data: 8 bits, 1 stop bit

7. Flow control (handshaking): None

8. Parity: None

9. Device address range: 1 – 247 (default address 017)

10. Termination: selectable, 120 ohms or none (default - none)

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Onicon System-30 MODBUS BTU Manual de usuario Pagina 28