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10-3

Ladder Logic (LAD) for S7-300 and S7-400

C79000-G7076-C504-02

10.2 Up-Down Counter

A positive edge (i.e. a change in signal state from 0 to 1) at input S of the

Up-Down Counter instruction sets the counter with the value at the Preset

Value (PV) input. A signal state of 1 at input R resets the counter. Resetting

the counter places the value of the count at 0. The counter is incremented by

1 if the signal state at input CU changes from 0 to 1 (that is, there is a

positive edge) and the value of the counter is less than 999. The counter is

decremented by 1 if the signal state at input CD changes from 0 to 1 (that is,

there is a positive edge) and the value of the counter is more than 0. If there

is a positive edge at both count inputs, both operations are executed and the

count remains the same. A signal state check for 1 at output Q produces a

result of 1 when the count is greater than 0; the check produces a result of 0

when the count is equal to 0.

Certain restrictions apply to the placement of the counter boxes (see

Section 6.1).

Table 10-1 Up-Down Counter Box and Parameters, with International Short Name

LAD Box Parameter Data Type Memory Area Description

no. COUNTER C

Counter identification number. The range

depends on the CPU.

Cno

CU BOOL I, Q, M, D, L Count up input CU

no.

S CUD

CD BOOL I, Q, M, D, L Count down input CD

CUD

QCU

S BOOL I, Q, M, D, L Set input for presetting counter

QCU

PV WORD I, Q, M, D, L Value in the range of 0 to 999 for

presetting counter (entered as

C#<value> to indicate BCD format)

CV_BCD

R BOOL I, Q, M, D, L Reset input

Q BOOL I, Q, M, D, L Status of the counter

CV WORD I, Q, M, D, L Current counter value (integer format)

CV_BCD WORD I, Q, M, D, L Current counter value (BCD format)

Description

Counter Instructions

1 2 ... 134 135 136 137 138 139 140 141 142 143 144 ... 317 318

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Siemens NAN 67 Series Manual de servicio Pagina 139