Modbus Register Map - GE DigitalFlow GC868 Programming Manual

April 2008
Procedure Options

MODBUS Register Map

1-46
After completing the above steps, the meter returns to the User
Program. Continue as follows:
•
To continue programming the meter, refer to the menu maps in
Appendix A and navigate to the desired menu. Then, proceed to
the appropriate section of this manual for instructions.
•
To leave the User Program and retain the previous settings,
[EXIT]
press and then press
programming changes will be discarded and you will be
returned to the data display.
•
To leave the User Program and return to measurement mode,
[EXIT]
press and then press
programming changes will be entered into the meter's memory,
and you will be returned to the data display.
When equipped with the optional MODBUS output card, the GC868
flow transmitter can send flow data and diagnostic information to a
flow computer (or SCADA) serially, using a Gould-type RTU
protocol. In this case, only the MODBUS function command, 3 (read
multiple registers), 6 (write multiple registers) is valid. The format for
the data exchange is as follows:
•
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 as follows:
•
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
To request specific parameters from the GC868 via the MODBUS,
the control system must enter the appropriate register number. Only
registers 1 through 90 are available for MODBUS communications,
while registers 508 through 512 are used by the GC868 to store the
MODBUS parameters. For details, see Table 1-9 on page 1-47.
Note: If you request Ch2 or AVE data from a 1-Channel meter, the
values will all be zero.
[F1] = NO
at the SAVE prompt. Any
[F2] = YES
at the SAVE prompt. Your
Programming Site Data