Response Modbus->Server Client, with error message:
|
Offs |
Bytes |
Type |
Modbus Description |
Contents(hex) |
ibaPDA Description |
|
|---|---|---|---|---|---|---|
|
MBAP |
00 |
2 |
UINT |
Transaction Identifier |
xx xx |
Mirror of request |
|
02 |
2 |
UINT |
Protocol Identifier |
00 00 |
0 |
|
|
04 |
2 |
UINT |
Cmd Length |
00 03 |
||
|
06 |
1 |
BYTE |
Unit ID |
xx |
Mirror of request |
|
|
Fcode |
07 |
1 |
BYTE |
Function code "Exception" |
0x80 + xx |
Mirror of function code with MSB=1 |
|
Data |
08 |
1 |
BYTE |
Error code |
xx |
Error code |
The received function code is copied and the highest-order bit set (MSB).
Example:
|
Function 03: Read Holding Registers |
|||
|---|---|---|---|
|
Request |
(hex) |
(hex) |
Response |
|
Trans ID |
00 03 |
00 03 |
Trans ID |
|
Prot ID |
00 00 |
00 00 |
Prot ID |
|
Cmd LEN |
00 06 |
00 03 |
Cmd LEN |
|
Unit ID |
01 |
01 |
Unit ID |
|
FCode |
03 |
83 |
FCode with error indication |
|
Start Adr (Hi) |
00 |
02 |
Error code |
|
Start Adr (Lo) |
6D |
||
|
No. Values (Hi) |
00 |
||
|
No. Values (Lo) |
04 |
||