Table of Contents
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SECTION 5
Modbus Communications
Procedure
Read this section if you are to communicate using the Modbus format.
5.1
5.2
5.3
5.4
Data Format.................................................................. 5-2
Command Frame................................................... 5-2
CRC-16 Calculation Example................... 5-3
Response Frame ................................................... 5-4
Normal Response Frame ......................... 5-4
Error Response Frame............................. 5-4
Error Codes ........................................................... 5-5
No Response............................................ 5-5
Function List ................................................................. 5-6
Variable Area ................................................................ 5-7
Addresses ................................................ 5-7
Number of Elements................................. 5-8
Set Values ................................................ 5-8
Detailed Description of the Services............................. 5-9
Read Variable Area ............................................... 5-9
Write Variable Area ............................................. 5-11
Operation Commands ......................................... 5-14
Echoback Test..................................................... 5-19
5-1
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