5.5.1 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 messages specifies the staring coil and quantity of coils to be read. Coil addresses start at zero, i.e. coil 33 is addressed as 32.
Example of a request to read coils 33-48 (Status Word) from slave device
01:
Field Name
Example (HEX)
Slave address
01 (frequency converter address)
Function
01 (read address)
Starting Address HI
00
Starting Address LO
20 (32 decimal)
No. of Points HI
00
No. of Points LO
10 (16 decimal)
Error Check (CRC)
-
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 eight, the remaining bits in the final data byte will padded with zeros (toward the high order and 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)
-
5.5.2 Force/Write Single Coil (05
HEX
)
Description
This function forces a 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, i.e. coil 65 is addressed as 64. 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 (coil no. 65)
Force Data HI
FF
Force Data LO
00 (FF 00 = ON)
Error Check (CRC)
-
Response
The normal response is an echo of the query, returned after the coil state has been forced.
VLT
®
Micro Drive FC 51 Operating Instructions
5 Modbus RTU
MG.02.A4.02 - VLT
®
is a registered Danfoss trademark
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