10 TROUBLESHOOTING
10.3.9 Troubleshooting when communication error "SIO" generates
Symptom |
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| Corrective action | MC |
| • Data does not match the | • Check if the Q series C24 and external device |
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| stop bit setting. |
| settings are the same. |
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| • | Transmission rate is too | • | Decrease the transmission rate and restart data |
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| fast and the next data is |
| communications. |
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| transmitted before the Q |
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| series C24 completes |
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| processing of the |
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| receive data. |
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| • Data larger than the | • Use DTR and DC control and interrupt |
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| receive buffer size was |
| transmission before the buffer becomes full. |
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| received. |
| Perform RS and CS control when the modem |
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| function is used. |
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| • | Increase the transmission interval and provide |
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| an ample PLC CPU read processing time. |
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| Note |
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• Communication error |
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| • The non procedure protocol stores the data |
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| received up to first the end code received, or |
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signal "SIO" turned on. |
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| fixed length data, to the non procedure |
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| receive buffer memory and turns on the Read |
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| Request signal to the PLC CPU. |
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| If the next data is sent while the Read |
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| Request signal is ON, the data is temporarily |
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| stored to the OS receive buffer. When the OS |
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| receive buffer becomes full, the Q series C24 |
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| skips the rest of the data and turns on the |
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| "SIO" LED. |
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| • With a multidrop link, | • | Connect the external devices and the Q series |
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| two or more devices |
| C24 in a 1:1 configuration and perform a |
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| transmitted data at the |
| communications test. Since data is transmitted |
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| same time. |
| simultaneously from two or more devices with a |
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| multidrop link when normal communications |
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| among all the devices is possible, interlock the |
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| devices so that cannot transmit simultaneously. |
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Bidirectional Non procedure
10 - 36 | 10 - 36 |