Specifications
7.10.1 Read Coil Status (01 HEX)
Description
This function reads the ON/OFF status of discrete outputs
(coils) in the frequency converter. Broadcast is never
supported for reads.
Query
The query message specifies the starting coil and quantity
of coils to be read. Coil addresses start at zero, i.e. coil 33
is addressed as 32.
Field Name Example (HEX)
Slave Address 01 (frequency converter address)
Function 01 (read coils)
Starting Address HI 00
Starting Address LO 20 (32 decimals) Coil 33
No. of Points HI 00
No. of Points LO 10 (16 decimals)
Error Check (CRC) -
Table 7.22 Example of a request to read coils 33-48
(Status Word) from slave device 01
Response
The coil status in the response message is packed as one
coil per bit of the data field. Status is indicated as: 1=ON;
0=OFF. The LSB of the first data byte contains the coil
addressed in the query. The other coils follow toward the
high order end of this byte, and from ‘low order to high
order’ in subsequent bytes.
If the returned coil quantity is not a multiple of 8, the
remaining bits in the final data byte are padded with zeros
(toward the high order end of the byte). The byte count
field specifies the number of complete bytes of data.
Field Name Example (HEX)
Slave address 01 (frequency converter address)
Function 01 (read coils)
Byte count 02 (2 bytes of data)
Data (coils 40-33) 07
Data (coils 48-41) 06 (STW=0607hex)
Error check (CRC) -
Table 7.23 Master Response
NOTICE
Coils and registers are addressed explicit
with an off-set of -1 in Modbus.
I.e. Coil 33 is addressed as Coil 32.
7.10.2 Force/Write Single Coil (05 HEX)
Description
This function forces the coil to either ON or OFF. When
broadcast, the function forces the same coil references in
all attached slaves.
Query
The query message specifies the coil 65 (parameter write
control) to be forced. Coil addresses start at zero. Force
Data = 00 00HEX (OFF) or FF 00HEX (ON).
Field Name Example (HEX)
Slave address 01 (frequency converter address)
Function 05 (write single coil)
Coil address HI 00
Coil address LO 40 (64 decimal) Coil 65
Force data HI FF
Force data LO 00 (FF 00 = ON)
Error check (CRC) -
Table 7.24 Query
Response
The normal response is an echo of the query, returned
after the coil state has been forced.
Field Name Example (HEX)
Slave address 01
Function 05
Force data HI FF
Force data LO 00
Quantity of coils HI 00
Quantity of coils LO 01
Error check (CRC) -
Table 7.25 Response
7.10.3 Force/Write Multiple Coils (0F HEX)
This function forces each coil in a sequence of coils to
either ON or OFF. When broadcast the function forces the
same coil references in all attached slaves.
The query message specifies the coils 17 to 32 (speed set-
point) to be forced.
Installation and Set-up VLT® HVAC Drive FC 102 Design Guide
MG16C102 - Rev. 2013-08-20 175
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