Version 3.11
| HPI Combi Flow User Guide |
57
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Modbus RTU and BACnet MSTP connection should be made via the RJ45 connector. The pin assignments are as shown in section
10.1. RS-485 Communications on page 56
Modbus RTU and BACnet MSTP networks require three conductors for best operation and to eliminate common mode voltages
on the drive terminals:
o RSR85+
o RS485-
o 0 Volt Common
Connection should be made using a suitable dual twisted pair, shielded cable, with a wave impedance of 120R.
Use one of the twisted pairs to connect to the RS485+ and RS485- of each drive.
Use one conductor of the remaining pair to connect together all the 0 volt common connection terminals.
The cable shield should be connected to a suitable clean ground point to prevent interference with the screen maintained as close
as possible to the cable terminations.
Do not connect the 0 Volt Common, RS485- or RS485+ to ground at any point.
Network terminating resistor (120R) should be used at the end of the network to reduce noise.
10.2. Modbus RTU Communications
10.2.1. Modbus Telegram Structure
The HP Combi Flow 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 first Register address as Register 0; therefore it may be necessary to convert the Register Numbers detail in section
10.2.2
by subtracting 1 to obtain the correct Register address.
10.2.2. Modbus Control & Monitoring Registers
The following is a list of accessible Modbus Registers available in the HP Combi Flow.
When Modbus RTU is configured 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.
Register
Number
Higher
Byte
Lower
Byte
Read
Write
Notes
1
Command Control Word
R/W
Command control word used to control the HP Combi Flow when operating with
Modbus RTU. The Control Word bit functions are as follows:
Bit 0 : Run/Stop command. Set to 1 to enable the drive. Set to 0 to stop the drive.
Bit 1 : Fast stop request. Set to 1 to enable drive to stop with 2nd deceleration ramp.
Bit 2 : Reset request. Set to 1 in order to reset any active faults or trips on the drive.
This bit must be reset to zero once the fault has been cleared.
Bit 3 : Coast stop request. Set to 1 to issue a coast stop command.
2
Command Speed Reference
R/W
Setpoint must be sent to the drive in Hz to one decimal place, e.g. 500 = 50.0Hz.
3
Reserved
R/W
No Function.
4
Command Ramp times
R/W
This register specifies the drive acceleration and deceleration ramp times used when
Fieldbus Ramp Control is selected (P5-08 = 1) irrespective of the setting of P1-12. The
input data range is from 0 to 60000 (0.00s to 600.00s).
6
Error code
Drive status
R
This register contains 2 bytes.
The Lower Byte contains an 8 bit drive status word as follows:
Bit 0 : 0 = Drive Disabled (Stopped), 1 = Drive Enabled (Running).
Bit 1 : 0 = Drive Healthy, 1 = Drive Tripped.
Bit 2: 0 = Auto, 1 = Hand.
Bit 3 : Inhibit.
Bit 4 : Service due.
Bit 5 : Standby.
Bit 6 : Drive Ready.
Bit 7 : 0 = Normal condition, 1 = Low or High Load condition detected.
The Upper Byte will contain the relevant fault number in the event of a drive trip. Refer
for a list of fault codes and diagnostic information.
10
Serial Communications
