5-1
SECTION 5
Modbus Communications
Procedure
Read this section if you are to communicate using the Modbus format.
5.1 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
5.2 Function List ................................................................. 5-6
5.3 Variable Area ................................................................5-7
Addresses ................................................ 5-7
Number of Elements.................................5-8
Set Values ................................................ 5-8
5.4 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
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