Appendix 4: VFD68Bxx and VFD68Cxx ModBus RTU RS485 Communications Bus Specifications - PENN Controls - VFD68Bxx - VFD68Cxx - VFD68Dxx - Three‐Phase Motor Speed Controller - VFD68 Three‐Phase Variable Frequency Drive

VFD68 Variable Frequency Drives Technical Bulletin

Product

Document revision

Revision date

2019-08-09

Part number

24-7664-3051

You must create a custom RS485 communication cable to connect the VFD68Bxx or VFD68Cxx to the head end of a ModBus RTU network.

Figure 1. VFD68Bxx and VFD68Cxx Identification of RJ45 Receptacle

Important: Do not connect pin 2 or pin 8 to a communication cable. Pin 2 and pin 8 of the RJ45 receptacle are connected to a power supply in the VFD68 drive. Connecting one or both of these pins to a communication cable may damage the VFD68 drive.

Table 1. VFD68Bxx and VFD68Cxx RJ45 Pin Identifications for Communications Bus
Pin Number	Name	Description
1	SG	Earth (ground) (connected to terminal 5)
2	—	Power supply
3	RDA	VFD receive (+)
4	SDB	VFD send (-)
5	SDA	VFD receive (+)
6	RDB	VFD send (-)
7	SG	Earth (ground) (connected to terminal 5)
8	—	Power supply

Using the Modbus RTU communication protocol, you can set the communication operation or parameter using the operation panel on the VFD68 drive. These parameters can be set when P.160 = 0.

Table 2. Parameters for ModBus RTU RS485 Communications
Parameter Number	Name	Default	Range
P.117	PU communication station number	0	0	No reply to the master¹
P.117	PU communication station number	0	1 to 247	VFD station number specification Set the VFD station numbers when two or more VFDs are connected to one computer.
P.118	PU communication speed	96	48, 96, 192, 384	Communication speed The setting value x 100 equals the communication speed. For example, if the communication setting is 96, the communication speed is 9600 bps.
P.120	PU communication parity check	2	0	Without parity check; Stop bit length: 2 bits
			1	With odd parity check; Stop bit length: 1 bit
			2	With even parity check; Stop bit length: 1 bit
P.122²	PU communication check time interval	9999	0
			0.1 to 999.8
			9999
P.343	Communication error count	0	___	Displays the number of communication errors during Modbus RTU communication (reading only)
P.502	Stop mode selection at communication error	0		At Fault Occurrence	Indication	Fault Output	At Fault Removal
			0	Coasts to stop	E.PUE	Output	Stop (E.PUE)
			1	Decelerates to stop	After stop, E.PUE	Output after stop	Stop (E.PUE)
			2	Decelerates to stop	After stop, E.PUE	Without output	Automatic restart functions
P.549	Protocol selection	0	0	VFD (computer link operation) protocol
P.549	Protocol selection	0	1	Modbus RTU protocol

¹ When Modbus RTU communication is performed from the master with address 0 (station number 0) set, broadcast communication is selected and the VFD does not send a response message. When a response from the VFD is necessary, set a value other than 0 in P.117. Some functions are invalid for broadcast communication.

² Specifications differ according to the date assembled.