Issue:
Function block to use in a Premium PLC for retrieving diagnostic information from a Modbus slave device
Product Line:
Premium PLC, Unity Pro
Resolution:
The SEND_REQ function block is used for retrieving diagnostic and maintenance information from a Modbus slave device....
Function block to use in a Premium PLC for retrieving diagnostic information from a Modbus slave device
Product Line:
Premium PLC, Unity Pro
Resolution:
The SEND_REQ function block is used for retrieving diagnostic and maintenance information from a Modbus slave device....
| Modbus Request | Function Code / Sub Function Code | Communication Function |
|---|---|---|
| Exception status | 16#07 | SEND_REQ |
| Diagnostics | 16#08/16#xx | SEND_REQ |
| Event counter | 16#0B | SEND_REQ |
| Connection event | 16#0C | SEND_REQ |
| Slave identification | 16#11 | SEND_REQ |
The diagnostics and maintenance information are shown below:
| Designation | Function code / sub-function code |
|---|---|
| Read exception status | 16#07 |
| Echo | 16#08 / 16#00 |
| Initialize module | 16#08 / 16#01 |
| Read the diagnostic registers of the PLC | 16#08 / 16#02 |
| Change end of frame delimiter (ASCII mode) | 16#08 / 16#03 |
| Switch to listening mode | 16#08 / 16#04 |
| Reset counters | 16#08 / 16#0A |
| Number of messages received without CRC error | 16#08 / 16#0B |
| Number of frames received with CRC error | 16#08 / 16#0C |
| Number of exceptional responses | 16#08 / 16#0D |
| Number of messages addressed to the PLC | 16#08 / 16#0E |
| Number of broadcast messages received | 16#08 / 16#0F |
| Number of correct responses | 16#08 / 16#10 |
| Number of messages received in listening mode | 16#08 / 16#11 |
| Number of invalid characters received | 16#08 / 16#12 |
| Read event counter | 16#0B |
| Read connection event | 16#0C |
| Read identification | 16#11 |
