Status of the counter:n Q is set to "1" if CV ≥ PV (current count ≥ preset value)n else Q = "0"Current count:n possible values: 0 ... 3276714.2.2 SFB 1 - CTD - Down-counterThe SFB 1 can be used as Down-counter. Here you have the following characteristics:n If the signal state at the down counter input CD changes from "0" to "1" (positiveedge), the current counter value is decremented by 1 and displayed at output CV.n When called for the first time with LOAD = "0" the counter value corresponds to thepreset value at input PV.n When the lower limit of -32767 is reached the counter will not be decremented anyfurther, i.e. all rising edges at input CU are ignored.n When a "1" is applied to the LOAD input then the counter is set to preset value PVirrespective of the value applied to input CD.n Output Q has signal state "1" if CV ≤ 0.n When it is necessary that the instances of this SFB are initialized after a restart, thenthe respective instances must be initialized in OB 100 with LOAD = 1 and PV =required preset value for CV.Parameter Declaration Data type Memory block DescriptionCD INPUT BOOL I, Q, M, D, L, con-stantCount inputLOAD INPUT BOOL I, Q, M, D, L, con-stantLoad input. LOAD takes precedenceover CD.PV INPUT INT I, Q, M, D, L, con-stantPreset valueQ OUTPUT BOOL I, Q, M, D, L Status of the counterCV OUTPUT INT I, Q, M, D, L Current countCount input:This counter is decremented by 1 when a rising edge (with respect to the most recentSFB call) is applied to input CU.Load input:When a 1 is applied to the LOAD input then the counter is set to preset value PV irre-spective of the value applied to input CD.Preset value:The counter is set to preset value PV when the input LOAD is “1”.QCVDescriptionParametersCDLOADPVVIPA SPEED7Integrated StandardSystem Function Blocks > SFB 1 - CTD - Down-counterHB00 | OPL_SP7 | Operation list | en | 18-30730
