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IM 01E21A02-03EN
Note 2: A transition to Cas, RCas, or ROut requires that initialization of the cascade connection
has been completed.
Note3:Incaseofthemodeshedding(thedatastatusofRCAS_IN,ROUT_INisBAD),it
transitionstothemodewhichhasbeenspeciedwithSHED_OPT.(Fordetails,referto
A5.17.1.)
A5.10 Bumpless Switching
BumplessswitchingisthefunctiontoallowthebumplessswitchofMODE_BLKandofoperation
output values at the cascade downstream without a sudden change in the control output.
Theactiontoperformabumplessswitchingdi󰀨ersdependingontheMODE_BLKvalues.
A5.11 Setpoint Limiter
Thesetpointlimiterfunctionistolimitthesettingsofthesetpoint(SP).
Theoperationofthesetpointlimiterdi󰀨ersbasedontheblockmodeofthefunctionblock.
A5.11.1 When PID Block Is in Auto Mode
Whentheblockmode(MODE_BLK)isAuto,thelimitersofthesetpoint(SP)inforcearehigh/low
limit and change-rate limit.
A5.11.1.1 High/Low Limit
Avalueexceedingthesethighlimit(SP_HI_LIM)cannotbesetforSP.
Avaluesmallerthanthesetlowlimit(SP_LO_LIM)cannotbesetforSP.
A5.11.1.2 Change-rate Limit
The change-rate limits are used to restrict the magnitude of changes in the SP value so as to
change the SP value gradually towards a new setpoint.
TheincreaseoftheSPvalueateachexecutionperiodofPID(periodofexecutionintheBlock
Header)islimitedtothevalueofSP_RATE_UPorless.
ThedecreaseoftheSPvalueateachexecutionperiodofPID(periodofexecutionintheBlock
Header)islimitedtothevalueofSP_RATE_DOWNorless.
A5.11.2 When PID Block Is in Cas or RCas Mode
ByselectingObeySPLimitsifCasorRCasinCONTROL_OPTS(seeSubsectionA5.13.1),the
setpoint(SP)high/lowlimitscanbeputintoforcewhentheblockmode(MODE_BLK)isCasor
RCas.
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