FIT controller operating with a Delta, VFD-M drive: an example on how to derive the correct registers & bitmasks.

FIT controller operating with a Delta, VFD-M drive: an example on how to derive the correct registers & bitmasks.

Below an example configuration between a Delta VFD-M drive and a FIT controller is explained. All configured parameters on both the FIT and the drive are listed. Additionally, at the end of this article, the used registers are documented to give an example of a possible drive configuration. This example inter alia helps in understanding how to select the correct registers and bitmasks.
For a more general explanation on how to use a FIT controller to control a Variable Speed Drive via modbus communication consult the following article.

VSD drive (VFD-M) configuration
  1. Pr.00 - Set the source of frequency command to be "master frequency determined by RS-485 Communication port" (03)
  2. Pr.01 - Set the source of operation command to be "operation determined by exernal control terminals,keypad STOP is effective" (01).
  3. Pr.03- Set the drive's Maximum Ouput Frequency(50Hz)
  4. Pr.04-Set the Maximum Voltage Frequency (50Hz)
  5. Pr.36- Set the Upper Bound of Output Frequency (50Hz)
  6. Pr.37- Set the Lower Bound of Outuput Frequency (25Hz)
  7. Pr.88-Communication address- 1 (default)
  8. Pr.89- Baud Rate -9600 bps (default)
  9. Pr.92-Communication protocal - MODBUS RTU MODE (8,O,1)
  10. Pr.157- Communication Mode Selection (MODBUS),please find this attached link for the detailed manual informaiton.
FIT controller configuration
  1. P10.01-Starter Mode-VSD
  2. P10.02-Control Mode-Pressure
  3. P10.24-Relay 5 - Running N/O
  4. P08.08- Output-Hzx100 (as the speed register operates with the Hz unit)
  5. P08.09- Slave Address-1
  6. P08.10- Speed Register- 8193 (decimal value)
  7. P08.11- Parity-Odd
  8. (FIT controller operates 1 stop bit by default , this is not configurable)
  9. P08.12-Baud Rate-9600
  10. P08.13- Fault Register-8448 (decimal value)
  11. P08.14- Fault Bitmask-255 (decimal value)
  12. P08.15- Reset Register-8194(decimal value)
  13. P08.16- Reset Bitmask- 2 （decimal value,when this register's bit=1,the reset funcition will be effective.）
Hardware wiring
  1. After configuring the FIT controller with the above settings, a communication cable between the VFD-M and FIT controller (X02) could be established.
  2. Connect the hardwire loop function digital input of the drive to the relay output of the FIT controller that is assigned as 'MAIN' contact.
  3. On the FIT controller, delete the present faults by navigating to the faults and push the red "C” button for 10s.
  4. Once the faults and alarms are gone, the FIT controller can be started, after the drive will be started as well.
VFD-M modbus documentation and register explanation
P08.08 - Output
The controller sends a speed value in Hz to the corresponding speed register (2001H) to tell it how fast it has to rotate. This drive speed register stores the speed as a number up to 2 decimal digits. In other words, if the drive is rotating at a speed of 50Hz, this register holds a value of 5000. In order to teach the controller the scale in which it should send its speed value, parameter P08.08 is used. The controller uses the speed values inserted in the configuration parameters (e.g. Maximum Hz) and multiplies it with the selected scaling size in P08.08. For example:
The controller sends out a speed value of 40Hz.
  1. P08.08 = Hzx10
    1. Sent speed value = 400
    2. The drive reads this speed as 4,00Hz which is too small, and not desired.
  2. P08.08 = Hzx100
    1. Sent speed value = 4000
    2. The drive reads this speed as 40,00Hz which is desired.
  3. P08.08 = Hzx1000
    1. Sent speed value = 40000
    2. The drive reads this speed as 400,00Hz which is too high, and not desired.
Therefore P08.08 is configured as Hzx100. If you are unable to determine the scaling size of the speed register, consult the drive manufacturer.

P08.09 Slave Address, P08.11 Parity, P08.12 Baud Rate
A drive has the ability to configure their communication protocol specifications via parameters. Spot those parameters, learn how they are configured and make sure that the parameters for both the controller and drive are synced / configured for the same values.


P08.15 Reset Register, P08.16 - Reset Bitmask
To reset a present fault on a drive, a certain 'Reset' bit has to be set from 'low' to 'high'. Often this reset bit is available in the control word. In this example, a seperate register is available. Find the register containing this 'reset' bit and insert it into P08.15 'Reset register'.
To "tell" the drive to reset its present fault, a high bit has to be present on the corresponding register bit. To be able to inform the controller which bit has to be sent, a bitmask is used. In this example, register 2002 contains 16 bits. Of which the second bit is the reset bit. However, the first bit of this register has another purpose (activating an external fault). In this case we do not want to activate other bits in the register, because this will result in unexpected behavior.
To reset the drive, register 2002 expects a value of '0100000000000000' binary, which equals '2' decimal. Therefore a value of 2 is to be inserted in the corresponding FIT parameter.

P08.13 Fault Register, P08.14 Fault Bitmask
There are to ways to read a fault. One way is to read a fault bit in the status word. Whenever the drive is faulted, this bit becomes high. To read the correct bit, a bitmask is again available.
A second way is to read the entire fault register. If this register contains a value of '00', no fault is present, as soon as a fault is present, the value in the drive will be different from '00'. For example, if an external fault is present, this register will contain the value '06'. Locate the status word or the fault register and insert it in P08.13.
The P08.14 fault bitmask will be used to "tell" the drive which bits are relevant to look at, and which are not. In this example, we want the controller to spot a drive fault as soon as the register is different from 00. Therefore, we want to take all the bits in the register into consideration. This register has a size of 8 bits. We want to look at all of those 8 bits. Therefore a bitmask of '1111 1111' binary = '255' decimal is to be used.


Extra info
Often a drive has multiple parameter groups. Be sure to know which parameter group is active on the drive, and how to address that parameter group accordingly.


To see if the drive is faulted, it is also possible to connect a digital output of the drive that will activate when it is tripped, and connect this output to a digital input of the FIT controller. The digital input function has then to be configured  accordingly.

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