Troubleshooting
Modbus Errors
Modbus errors are typical protocol errors defined by fieldbus specification. The fieldbus error code shown is returned to the PLC when the error condition occurs.
Code | Name | Cause |
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1 | Illegal Function | Request function is not supported. | Use supported Modbus functions: | |
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| • | Read Holding Register |
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| • | Write Holding Register |
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| • Write Multiple Holding Registers | |
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2 | Illegal Data Address | Exceeded maximum register count | Request 121 or fewer registers at a time. | |
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| of 121 registers. |
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| No valid property mapped to the | Verify that the device has valid mapping. | |
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| requested Modbus register. | See MBTCP Modbus Error for 4 red | |
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| flashes. | |
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| Write Holding Register(s) returns | Verify that the end device is online. | |
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| set property error. |
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3 | Illegal Data Value | Not implemented. | ||
4 | Slave Device Fail | Not implemented. | ||
5 | Acknowledge | Not implemented. | ||
6 | Slave Device Busy | Not implemented. | ||
8 | Memory Parity Error | Not implemented. | ||
10 | Gatweay Path Unavailable | Not implemented. | ||
11 | Gateway Target Fail | An active system error exists. | Refer to system errors table. | |
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255 |
| Unspecified |
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8 | 334183A |
