Axpert-Eazy AC Variable Frequency Drive
11.13
10
11
section.
If the query is received properly then the response is returned as below.
Number
1 01h First byte is the address of the modbus slave device referred as station
number.
2 03h Indication of read operation
3 02h No. of data bytes packed after byte 3.
4 01h Data Byte High
5 F4h Data Byte Low. Byte number 4 and 5 has right justified packed value of
the required parameter.
6 CRC Low CRC Low Byte
7 CRC High CRC High Byte. The High and Low bytes are reversed in CRC
transmission. The method of calculating CRC is described in the next
section.
The data received as packed data in bytes 4 and 5. Hence received value is 01F4h = 500d. So the
final value of the parameter is 500/10 = 50.0 because parameter 40003 has resolution of 1 digit after
decimal point.
5.2 Read Multiple Parameter
This query is used for single parameter read. Total 8 bytes are transmitted. 3.5-character times delay
is provided at the start and end of the query for indication of starting and ending of query.
For example if you want to read parameter 40001 to 40010 then the format of query is as below.
Number
1 01h First byte is the address of the modbus slave device referred as station
number.
2 03h Indication of read operation
3 00h Starting address High byte
4 00h Starting Address Low byte. Parameter 40001 is addressed as 0000h.
Byte 3 and 4 has right justified packed value of parameter number.
5 00h No of parameters High Byte
6 0Ah No of parameters Low Byte. For 10 parameters to be read then 0Ah is
used.
7 CRC Low CRC Low Byte
8 CRC High CRC High Byte. The High and Low bytes are reversed in CRC
transmission. The method of calculating CRC is described in the next
section.
If the query is received properly then the response is returned as below.
Number
1 01h First byte is the address of the modbus slave device referred as station
number.
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