Coil Register Addressing - Danfoss VLT AQUA Drive FC 202 Design Manual

RS-485 Installation and Set...

7.8.8 Coil Register Addressing

In Modbus, all data are organised in coils and holding registers. Coils hold a single bit, whereas holding registers hold a 2
byte word (16 bits). All data addresses in Modbus messages are referenced to zero. The first occurrence of a data item is
addressed as item number zero. For example: The coil known as 'coil 1' in a programmable controller is addressed as coil
0000 in the data address field of a Modbus message. Coil 127 decimal is addressed as coil 007EHEX (126 decimal).
Holding register 40001 is addressed as register 0000 in the data address field of the message. The function code field
already specifies a 'holding register' operation. Therefore, the '4XXXX' reference is implicit. Holding register 40108 is
addressed as register 006BHEX (107 decimal).
Coil number Description
1–16 Frequency converter control word (see Table 7.13)
17–32 Frequency converter speed or set-point reference Range 0x0–0xFFFF (-200% ...
~200%)
33–48 Frequency converter status word (see Table 7.13)
49–64 Open loop mode: Frequency converter output frequency Closed loop mode:
Frequency converter feedback signal
65 Parameter write control (master to follower)
0 = Parameter changes are written to the RAM of the frequency converter
1 =Parameter changes are written to the RAM and EEPROM of the frequency
converter.
66-65536 Reserved
Table 7.12 Coils and Holding Registers
MG20Z202
Design Guide
Danfoss A/S © Rev. 06/2014 All rights reserved.
Signal direction
Master to follower
Master to follower
Follower to master
Follower to master
Master to follower
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