Quality Bit for FC222 Analog In Channel , FC 121, FC45,FC42,FC30
I have realized in customer configuration that they have defined some controllers many logic gets the information from others controllers because of that they are using FC 222 Analog In channel which it has quality bit as one of the features , status error channel is not inhibited .In another node there are using FC121 to get the values from another node. if there are some inputs or one of them with bad data status
Is the value frozen from AI/L and keep the value until the problem to be fixed ? and does the logic use the last good quality value until the problem to be fixed ?
If we have DO/L FC 45 configured in one node and in another node DI/L FC 42 ( getting the value) if source node has communication problem
Is the value frozen until the problem is fixed ? , and does the logic use the last good quality value until the problem to be fixed ? we know that FC 45 has output and quality
Is the same for AO/L FC 30 and AI/L FC 121?
Thanks for your support
Appendix K of the Function code reference manual deals with point quality in detail. For peer to peer communications, if the input data cannot cannot be read for 8 successive IO scan cycles the point quality flag is set to bad. After the point quality flag is set to indicate bad quality, the receiving module retains and uses the last good value that was obtained. This applies to both digital and analog signals imported by any of the loop or bus input function codes.
In your case.
- The FC121 output in the receiving module is held at the last good value with the bad quality flag set until the incoming point quality returns to good.
- The FC42 output in the receiving module is held at the last good value with the bad quality flag set until the incoming point quality returns to good.
- The TSTQ (FC31) can be used in the receiving module to initiate logic when point quality goes bad rather than just using the last good value. Examine the logic for the presence of TSTQ blocks to determine exactly how the logic will behave when inputs are bad quality.
- The channel input quality of the FC222 is also propagated to the receiving module so the receiving module FC121 point quality will be bad if the communications between the modules has failed or if the FC222 channel input is bad quality.
- If the input to the DO/L includes quality, (eg FC84, FC97) this is also propagated to the receiving module so the receiving module FC42 point quality will be bad if the communications between the modules has failed or the DO/L input is bad quality.
- The last good value in the receiving module is volatile. I.E. If the receiving module is reset or put into configure the bad quality values will default to 0.0 or 0 and bad quality, depending the point type, when the module returns to execute.
Source: 2VAA000844R0001, ABB Ability™ Symphony® Plus S+ Engineering Function code reference User manual, Appendix K