Panametrics DigitalFlow XMT868i, Programming Manual

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DigitalFlow™ XMT868i Programming Manual 37
Chapter 1. Programming Site Data
1.4.3.2 Setting Up MODBUS (RS485) and MODBUS/TCP Communications
When equipped with an optional MODBUS output card, the XMT868i 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 XMT868i 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 XMT868i MODBUS communications settings chosen in the next four steps must match those of the
MODBUS control system.
4. Scroll to the desired MODBUS Baud Rate and press
[Enter]
.
IMPORTANT: The MODBUS./TCP interface requires a baud rate of 9600.
5. Scroll to the MODBUS Parity and press
[Enter]
.
6. Scroll to the MODBUS Stop Bits and press
[Enter]
.
7. Enter a MODBUS Meter Address (between 1 and 254) and press
[Enter]
. (The default address is 1.)
The meter returns to the Global PROGRAM prompt. Press [Escape] twice to return to the Keypad Program, and a third
time to return to the meter display .
IMPORTANT: You must reboot the XMT868i to load the new settings.
Refer to the section Requesting Parameters Using MODBUS on page 39 to retrieve data from the XMT868i using
MODBUS.