11.10.8 Coil Register Addressing
In Modbus, all data are organized in coils and holding
registers. Coils hold a single bit, whereas holding registers
hold a 2-byte word (i.e. 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 Signal Direction
1-16 Frequency converter control word (see table below) Master to slave
17-32 Frequency converter speed or set-point reference Range 0x0 – 0xFFFF (-200% ...
~200%)
Master to slave
33-48 Frequency converter status word (see table below) Slave to master
49-64 Open loop mode: Frequency converter output frequency Closed loop mode:
frequency converter feedback signal
Slave to master
65 Parameter write control (master to slave) Master to slave
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
Coil 0 1
01 Preset reference LSB
02 Preset reference MSB
03 DC brake No DC brake
04 Coast stop No coast stop
05 Quick stop No quick stop
06 Freeze freq. No freeze freq.
07 Ramp stop Start
08 No reset Reset
09 No jog Jog
10 Ramp 1 Ramp 2
11 Data not valid Data valid
12 Relay 1 off Relay 1 on
13 Relay 2 off Relay 2 on
14 Set up LSB
15 Set up MSB
16 No reversing Reversing
frequency converter control word (FC profile)
Coil 0 1
33 Control not ready Control ready
34 frequency converter not
ready
frequency converter ready
35 Coasting stop Safety closed
36 No alarm Alarm
37 Not used Not used
38 Not used Not used
39 Not used Not used
40 No warning Warning
41 Not at reference At reference
42 Hand mode Auto mode
43 Out of freq. range In frequency range
44 Stopped Running
45 Not used Not used
46 No voltage warning Voltage warning
47 Not in current limit Current limit
48 No thermal warning Thermal warning
frequency converter status word (FC profile)
RS-485 Installation and Set... FC 300 Design Guide
264 MG.33.BD.02 - VLT
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