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14-14

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

C79000-G7076-C504-02

14.12 Negate Floating-Point Number

The Negate Floating-Point Number instruction reads the contents specified in

the input parameter IN and inverts the sign bit, that is, the instruction

changes the sign of the number (for example from 0 for plus to 1 for minus).

The bits of the exponent and mantissa remain the same. The output

parameter OUT provides the result. ENO and EN always have the same

signal state.

Certain restrictions apply to the placement of the Negate Floating-Point

Number conversion box (see Section 6.1).

Table 14-12 Negate Floating-Point Number Box and Parameters

LAD Box Parameter Data Type Memory Area Description

NEG R

EN BOOL I, Q, M, D, L Enable input

NEG

EN ENO

ENO BOOL I, Q, M, D, L Enable output

IN OUT

IN REAL I, Q, M, D, L Input value

OUT REAL I, Q, M, D, L The result is the negated form of the

input value.

Status Word Bits

I 0.0

If the signal state of input I 0.0 is 1, the conversion

is executed. The value of memory double word

MD8 is provided at OUT in memory double word

MD12 with the opposite sign, as shown in the

following example:

MD8 = +6.234 x 10

–3

→ MD12 = –6.234 x 10

–3

If the conversion is not executed, the signal state

of output Q 4.0 is 1 (ENO = EN).

Q 4.0

NEG_R

EN ENO

MD8 MD12

BR CC 1 CC 0 OV OS OR STA RLO FC

Write x – – – – 0 x x 1

NOT

OUT

Function is executed (EN = 1):

Figure 14-12 Negate Floating-Point Number

Move and Conversion Instructions

1 2 ... 187 188 189 190 191 192 193 194 195 196 197 ... 317 318

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