DigitalFlow™ XGS868i Programming Manual
37
Chapter 1. Programming Site Data
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.
Summary of Contents for DigitalFlow XGS868i
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