Specifications

IEC 1131-3 Instructions
10-16
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
Down Counter
The Down Counter 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.
Note
Since 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.)
Table 10-5 Count Down Counter Operands and Data Types
Inputs/Outputs
Operands Data Types
CD (FBD) I, Q, M, SM, V, S, L, T, C, Power Flow BOOL
LD (FBD) I, Q, M, SM, V, S, L, T, C, Power Flow BOOL
PV (LAD, FBD) VW, IW, QW, MW, SMW, LW, SW, AIW, AC, Constant, *VD, *AC,
*LD
INT
Q (LAD & FBD) I, Q, M, SM, V, S, L BOOL
CV (LAD & FBD) VW, IW, QW, MW, SW, LW, AC, *VD, *AC, *LD INT
xxx C0 through C255 CTD
L
A
D
F
B
D
xxx
CTD
CD
LD
PV
Q
CV
222 224
333
221