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1.9.3b
Setting Up MODBUS Communications
When equipped with an optional MODBUS output card, the XGS868i can transmit flow data serially to a flow
computer, or SCADA, using a Gould-type RTU protocol. Thus only the MODBUS function command, 3 (read multiple
registers), 6 (write multiple registers) is valid. The XGS868i uses the following format for the data exchange:
•
The Send command (initiated by the host flow computer or controller) comes in the form:
[time delimiter]<Addr><3><First Register MSB>
<First Register LSB> <Register Count MSB>
<Register Count LSB><CRC Low><CRC High>[time delimiter]
•
The Response (initiated by the host flow computer or controller) comes in the form:
[time delimiter]<Addr><3><Byte count><Data...........>
<CRC Low><CRC High>[time delimiter]
The format for the returned data types is:
•
Integer (16 bit Integer) <MSB><LSB>
1 Register - 16 bit integer
•
Integer (32 bit IntegerI) <MSB><LSB><LSB><LSB>
2 Register - 32 bit integer
•
Floating Point (FP)<EXP><MAN><MAN><MAN>
2 Registers - 32 bit IEEE floating point number
Use the steps below to configure MODBUS communications:
IMPORTANT:
The XGS868i MODBUS communications settings chosen in the next four steps must match those of the
MODBUS control system.
1. Scroll to the desired MODBUS Baud Rate and press [Enter].
2. Scroll to the MODBUS Parity and press [Enter].
3. Scroll to the MODBUS Stop Bits and press [Enter].
4. Enter a MODBUS Meter Address (between 1 and 254) and press [Enter]. (The default address is 1.)
IMPORTANT:
You must reboot the XGS868i to load the new settings.
Procedure Options
After completing the above steps, the XGS868i returns to the Global PROGRAM window. Do one of the following:
•
Refer to the section Requesting Parameters Using MODBUS on the following page to retrieve data from the
XGS868i using MODBUS.
•
To continue regular programming, refer to Appendix A, Menu Maps, to navigate to the desired menu.
To leave the Keypad Program, press [Escape] three times.
•
DigitalFlow™ XGS868i Programming Manual
Chapter 1. Programming Site Data
37
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