An Omron CT021 IORD read can return error 350, reported as “invalid control code,” even when the selected control code matches the intended counter. In the documented case, the corrective actions were to configure the counter for circular operation with the unit’s DIP switches and set the required range limits.
Separate the Confirmed Settings from the Unknowns
| Item | Evidence-supported detail | Engineering decision |
|---|---|---|
| Error | 350, invalid control code | Check the counter selection and hardware mode before changing memory destinations or trigger conditions. |
| Counter 1 control code | #1F01 | Use when requesting counter 1. |
| Counter 2 control code | #2F01 | Do not substitute this code when reading counter 1. |
| Required configuration | Circular-counter DIP-switch setting and configured range limits | Complete both settings before retrying the rate read. |
| Unit number | A mismatched unit number was found in a separate attempt | Verify that the IORD source specification addresses the actual unit; correcting this alone did not resolve that attempt. |
The evidence does not fully define the source-word encoding, rate-value word count, or all CT021 switch positions. Confirm those details in the applicable CT021 manual instead of deriving them from the hexadecimal examples.
Check the IORD Request
The failing counter 1 request was recorded as follows:
C: #1F01
S: #00020008
D: D2
Requested length: 2 wordsChanging the destination and increasing the request from two words to three did not correct the error. Likewise, executing the instruction continuously, from P_On, or from a P_1s pulse did not resolve it. These results direct troubleshooting toward the counter number, addressed unit, operating mode, and range configuration rather than the destination register or execution trigger.
Correct and Verify the CT021 Configuration
- Confirm which physical counter supplies the signal. Select #1F01 for counter 1 or #2F01 for counter 2.
- Verify that the machine or unit number encoded by the IORD source matches the CT021 unit number.
- Set the applicable counter DIP switch for circular-counter operation.
- Configure the counter’s range limits. The cited manual locations for the circular and range-related settings are Sections 4-5-1-2 and 4-5-3-2.
- Retry the IORD read and confirm that error 350 clears and that the destination receives the rate value.
The application signal was described as 10 kHz at zero scale and approximately 15 kHz at full scale, while the counter was configured with a 500 kHz noise-filter setting and up/down circular counting. These values describe the reported installation; they do not establish the missing range-limit values. Derive those limits from the application and the CT021 manual rather than copying unspecified settings.
FAQ
What does CT021 IORD error 350 mean?
It was reported as “invalid control code.” Verify the selected counter code, addressed unit number, circular-counter DIP-switch setting, and configured range limits.
Which IORD control code reads CT021 counter 1?
Use #1F01 for counter 1. The evidence identifies #2F01 as the corresponding selection for counter 2.
Will reading three words fix CT021 error 350?
Not in the documented case; changing the read from two words to three did not help. Correct the circular-counter switch setting and range limits, then verify the unit number and retry the read.