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
Variable Read, Multiple .........................................5-9
Variable Write, Multiple........................................ 5-11
Variable Write, Single/Operation Command........ 5-14
Echoback Test..................................................... 5-20