Down Counter Counters

Inputs/Outputs Operands Data Types
CD (LAD) Power Flow BOOL
CD (FBD) I, Q, M, SM, V, S, L, T, C, Power Flow BOOL
LD (LAD) Power Flow BOOL
LD (FBD) I, Q, M, SM, V, S, L, T, C, Power Flow BOOL
PV VW, IW, QW, MW, SMW, LW, SW, AIW, AC, Constant, *VD, *AC, *LD INT
Q I, Q, M, SM, V, S, L BOOL
CV VW, IW, QW, MW, SW, LW, AC, *VD, *AC, *LD INT
xxxx (LAD & FBD) Constant (C0 C255) CTD

Memory Ranges ENO Errors Instruction Support for S7-200 CPUs SIMATIC/International Mnemonics
The Down Counter (CTD) function block counts down from the preset value on the rising edges of the Count Down (CD) input. When the current value (CV) is equal to zero, the counter output bit (Q) turns on. The counter resets and loads the current value (CV) with the preset value (PV) when the load input (LD) is enabled. The Down Counter stops counting when it reaches zero.

Counter ranges:xxx=C0 through C255

Note:

Because there is one current value for each counter, do not assign the same number to more than one counter. (Up Counters, Down Counters, and Up/Down Counters access the same current value.)