Modbus Registers; Compatibility; Ensuring Safe And Successful Control; Configuring Soft Starter Parameters - Danfoss VLT Compact Starter MCD 201 Installation Manual

Modbus Registers

7 Modbus Registers
NOTICE
All references to registers mean the registers within the
module unless otherwise stated.

7.1 Compatibility

The Modbus TCP Module supports 2 modes of operation:
•
In standard mode, the module uses registers
defined in the Modbus Protocol Specification.
•
In legacy mode, the module uses the same
registers as the Modbus Module from Danfoss.
Some registers differ from those specified in the
Modbus Protocol Specification.
7 7
The values of bit 15 in register 40001 determine the
operating mode.
•
Standard mode: Set bit 15 = 1. Bits 0–7 of register
40001 are used for command.
•
Legacy mode: Set bit 15 = 0. The remaining bits
of register 40001 are reserved.
Examples
10000000 00000001 = Start the motor (standard mode).
10000000 00000000 = Stop the motor (standard mode).
00000000 xxxxxxxx = Switch to legacy mode. The module
ignores the remaining bits in register 40001 and checks
the value in register 40002.

7.2 Ensuring Safe and Successful Control

Data written to the Modbus TCP Module remains in its
registers until the data is overwritten or the module is
reinitialized. The Modbus TCP Module does not transfer
successive duplicate commands to the soft starter.
•
If the soft starter is started via fieldbus communi-
cations but stopped via the LCP or a remote
input, an identical start command cannot be used
to restart the soft starter.
•
If the soft starter may also be controlled via the
LCP or the remote inputs (and via fieldbus
communications), a control command should be
immediately followed by a status query to
confirm that the command has been actioned.
12
Modbus TCP Module

7.3 Configuring Soft Starter Parameters

Parameter management is always multiple write of the
entire parameter block.
When configuring parameters in the soft starter, the PLC
must be programmed with the correct values for all
parameters. The card updates every parameter in the soft
starter to match the values in the PLC.
UNPREDICATABLE BEHAVIOR
Do not change the default values of parameter group 20-
** Factory Parameters. Changing these values may cause
unpredictable behavior in the soft starter.

7.4 Standard Mode

7.4.1 PLC Configuration

The PLC must be configured to map registers within the
module to addresses within the PLC.
Illustration 7.1 Example Mapping of PLC Registers to Registers
within the Modbus TCP Module (Target)
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CAUTION
MG17N102