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PACMotion VFD Syllabus
GFK-3167B
Modbus RTU Process Data Exchange
The mapping of Process Data Output/Input to Modbus RTU Registers is shown below.
Process Data Word
PDO1
PDO2
PDO3
PDO4
PDI1
PDI2
PDI3
PDI4
6.1
Modbus RTU Connection Timeout
The VFD Modbus RTU interface allows the user to set the Communication Loss Timeout
and Communication Loss Action values. These parameters are at addresses P5-05 and P5-
06 respectively. The Timeout units are 1 = 0.1 sec and the valid range is from 0.0 (disable)
to 5.0 seconds. A setting of 0.0 seconds will allow the VFD to continue running if
communications is lost.
6.2
Drive Parameter Access
The Modbus RTU Interface allows the user to read/write the drive parameters. To perform
this function, the user can directly access the parameter. Simply add the parameter
number to the Modbus offset of 400000.
For example:
Read parameter P1-01 (Maximum Frequency), perform the following
Read Modbus RTU Register 400101 value (scaling in 0.1 Hz).
Write parameter P1-01 (Maximum Frequency) = 60.0 Hz, perform the following
Write to Modbus RTU Register 400101 value = 600 (scaling in 0.1 Hz)
2
Modbus Clients may address the first Modbus register as register 300001/400001. This assumes an address offset starting at 1. For
Clients that use zero based addressing just subtract 1.
Modbus RTU Serial Demo (Note 3)
Modbus RTU Register
2
300001
300002
300003
300004
400001
400002
400003
400004
Section 6
December 2020
22
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