12
1 FRAME SPECIFICATIONS
1.3 Protocol Data Unit Formats Grouped by Function
■ Response message format
The format of the response message sent from a slave to the master varies depending on whether the processing performed
by the slave completed successfully or completed with an error.
In the MODBUS standard function, the formats when completed successfully and completed with an error are described in the
response message format.
Storage locations of exception code and error code
When processing on a slave is completed with an error, an exception code is sent to the master.
For details on exception codes, refer to the following.
Page 50 EXCEPTION CODES
Exception codes are also stored in the buffer memory of modules.
The detailed cause is detected as an error by modules.
For details on the buffer memory and errors of modules, refer to the following.
MELSEC iQ-R Ethernet User's Manual (Application)
MELSEC iQ-R Serial Communication Module User's Manual(Application)
(H) (L) (H) (L)
01H
(H) (L) (H) (L) (H)
(L)
(30H) (31H) (30H) (30H) (36H) (45H) (30H) (30H) (33H) (46H)
0 FE61 30000
(006EH) (003FH)
Start coil number specification
Data
Number of read points
Function code
Data
Start coil number specification
Number of read points
Function code
(RTU mode)
(ASCII mode)
Convert RTU mode to ASCII mode
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