<Appendix 5. PID Block>
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A5.16 AUTO Fallback
AUTO fallback denotes a mode in which the PID block changes a mode from Cas to Auto and
continues automatic PID control with the user-set setpoint.
A5.16.1 Condition of AUTO Fallback
The condition is established when the data status of the cascade setpoint (CAS_IN.Status) is
BAD,
(Excluding when BYPASS)
A5.16.2 Specification of AUTO Fallback
Specifies “Target to next permitted mode if BAD CAS IN” with STATUS_OPTS.
(Also, specify the destination of transition to AUTO with MODE_BLK.Permitted.)
A5.17 Mode Shedding upon Computer Failure
When the data status of RCAS_IN or ROUT_IN falls to BAD while the PID block is running in the
RCas or ROut mode, the mode shedding functions. If the RCAS_IN data is not renewed within
the time specified by SHED_RCAS in the resource block, the data status of RCAS_IN falls to
Bad.
At this time, change to the mode (Mode Shedding) specified in SHED_OPT.