Table of Contents
Advertisement
5.5 Examples
The following examples illustrate various Modbus RTU commands. If an error occurs, please refer to the Exception Codes section.
5.5.1 Read Coil Status (01
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
Slave address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
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
Slave address
Function
Byte count
Data (Coils 40-33)
Data (Coils 48-41)
Error Check (CRC)
5.5.2 Force/Write Single Coil (05
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
Slave address
Function
Coil Address HI
Coil Address LO
Force Data HI
Force Data LO
Error Check (CRC)
)
HEX
)
HEX
AF-60 LP™ Micro Drive Operating Instructions
Example (HEX)
01 (frequency converter address)
01 (read address)
00
20 (32 decimal)
00
10 (16 decimal)
-
Example (HEX)
01 (frequency converter address)
01 (read coils)
02 (2 bytes of data)
07
06 (STW = 0607hex)
-
Example (HEX)
01 (frequency converter address)
05 (write single coil)
00
40 (coil no. 65)
FF
00 (FF 00 = ON)
-
DET-579A
5
33
Advertisement
Table of Contents
