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10.2.2.
Modbus Control & Monitoring Registers
The following is a list of accessible Modbus Registers available in the ACS255.
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 providing that Modbus RTU is selected as the primary command source (1103
PRIMARY COMMAND SOURCE MODE = 4).
Register 3 can be used to control the output torque level providing that
o
The drive is operating in Vector Speed or Vector Torque motor control modes (9903 MOTOR CONTROL MODE = 1 or 2).
o
The torque controller reference / limit is set for ‘Fieldbus’ (2014 TORQUE CONTROL REFERENCE / LIMIT SOURCE = 3).
Register 4 can be used to control the acceleration and deceleration rate of the drive providing that Fieldbus Ramp Control is enabled
(2210 FIELDBUS RAMP CONTROL = 1).
Registers 6 to 24 can be read regardless of the setting of parameter 1103 PRIMARY COMMAND SOURCE MODE.
Register
Number
Upper Byte
Lower Byte
Read
Write
Notes
1
Command Control Word
R/W
Command control word used to control the ACS255 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 2
nd
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
Command Torque Reference
R/W
Setpoint must be sent to the drive in % to one decimal place, e.g. 2000 = 200.0%
4
Command Ramp times
R/W
This register specifies the drive acceleration and deceleration ramp times used when
Fieldbus Ramp Control is selected (2210 FIELDBUS RAMP CONTROL = 1) irrespective of
the setting of 1103 PRIMARY COMMAND SOURCE MODE. 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
The Upper Byte will contain the relevant fault number in the event of a drive trip.
Refer to section 13.1 on page 62 for a list of fault codes and diagnostic information
7
Output Frequency
R
Output frequency of the drive to one decimal place, e.g.123 = 12.3 Hz
8
Output Current
R
Output current of the drive to one decimal place, e.g.105 = 10.5 Amps
9
Output Torque
R
Motor output torque level to one decimal place, e.g. 474 = 47.4 %
10
Output Power
R
Output power of the drive to two decimal places, e.g.1100 = 11.00 kW
11
Digital Input Status
R
Represents the status of the drive inputs where Bit 0 = Digital Input 1 etc.
20
Analog 1 Level
R
Analog Input 1 Applied Signal level in % to one decimal place, e.g. 1000 = 100.0%
21
Analog 2 Level
R
Analog Input 2 Applied Signal level in % to one decimal place, e.g. 1000 = 100.0%
22
Pre Ramp Speed Reference
R
Internal drive frequency setpoint
23
DC bus voltages
R
Measured DC Bus Voltage in Volts
24
Drive temperature
R
Measured Heatsink Temperature in °C
10.2.3.
Modbus Parameter Access
All User Adjustable parameters are accessible by Modbus, except those that would directly affect the Modbus communications, e.g.
5302 DRIVE FIELDBUS ADDRESS
5303 Modbus RTU Baud Rate
5304 Modbus Data Format
5305 CAN Open Baud Rate
All parameter values can be read from the drive and written to, depending on the operating mode of the drive – some parameters cannot be
changed whilst the drive is enabled for example.
When accessing a drive parameter via Modbus, the Register number for the parameter is in the order of the long parameter list (See page 43
with the first register being 129 (Parameter 0401 TRIP HISTORY LOG).
Modbus RTU supports sixteen bit integer values, hence where a decimal point is used in the drive parameter; the register value will be multiplied
by a factor of ten,
E.g. Read Value of parameter 2008 = 500, therefore this is 50.0Hz.
For further details on communicating with ACS255 using Modbus RTU, please refer to your local ABB representative.
