Emerson PACMotion VFD Series - Modbus RTU and CAN Open Communications

78 PACMotion VFD AC Variable Speed Drive User Guide GFK-3111A
Modbus RTU Communications
Modbus Telegram Structure
The PACMotion VFD supports Master / Slave Modbus RTU communications, using the 03 Read Multiple
Holding Registers and 06 Write Single Holding Register commands and 16 Write Multiple Holding Registers
(Supported for registers 1 – 4 only). Many Master devices treat the rst Register address as Register 0;
therefore it may be necessary to convert the Register Numbers detailed in section Modbus Control &
Monitoring Registers by subtracting 1 to obtain the correct Register address.
Modbus Control & Monitoring Registers
The following is a list of accessible Modbus Registers available in the PACMotion VFD.
• When Modbus RTU is congured as the Fieldbus option, all of the listed registers can be accessed.
• Registers 1 and 2 can be used to control the drive provided that Modbus RTU is selected as the primary
command source (P1-12 = 4) and no Fieldbus Option Module is installed in the drive Option Slot.
• Register 4 can be used to control the acceleration and deceleration rate of the drive providing that
Fieldbus Ramp Control is enabled (P5-07 = 1).
• Registers 6 to 24 can be read regardless of the setting of P1-12.