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19-4

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

C79000-G7076-C504-02

19.3 Result Bits

You can use the Result Bit instructions to determine the relationship of the

result of a math function to zero, that is, if the result is >0, <0, >=0, <=0,

==0, or <>0. This instruction uses a comparison to zero as its address (see

Table 19-1). Internally, the CPU goes to the condition code bits of the status

word (CC 1 and CC 0, see Section 6.3) and checks the combination of signal

states in these locations. The combination tells the CPU the relationship of

the result to 0. If the comparison condition indicated in the address is

fulfilled, the result of this signal state check is 1.

When used in series, this instruction combines the result of its check with the

previous result of logic operation (RLO) according to the And truth table

(see Section 6.2 and Table 6-8). When used in parallel, this instruction

combines the result of its check with the previous RLO according to the Or

truth table (see Section 6.2 and Table 6-9).

Table 19-1 Result Bit Elements and Their Negated Forms

LAD Element Description

> 0

The Result Bit Greater Than 0 instruction determines whether or not the result of a math

function is greater than 0. This instruction checks the combination in the CC 1 and CC 0

(condition code) bits of the status word to determine the relationship of a result to 0.

< 0

The Result Bit Less Than 0 instruction determines whether or not the result of a math

function is less than 0. This instruction checks the combination in the CC 1 and CC 0

(condition code) bits of the status word to determine the relationship of a result to 0.

> = 0

The Result Bit Greater Equal 0 instruction determines whether or not the result of a math

function is greater than or equal to 0. This instruction checks the combination in the CC 1

and CC 0 (condition code) bits of the status word to determine the relationship of a result

to 0.

< = 0

The Result Bit Less Equal 0 instruction determines whether or not the result of a math

function is less than or equal to 0. This instruction checks the combination in the CC 1

and CC 0 (condition code) bits of the status word to determine the relationship of a result

to 0.

== 0

The Result Bit Equal 0 instruction determines whether or not the result of a math

function is equal to 0. This instruction checks the combination in the CC 1 and CC 0

(condition code) bits of the status word to determine the relationship of a result to 0.

< > 0

The Result Bit Not Equal 0 instruction determines whether or not the result of a math

function is not equal to 0. This instruction checks the combination in the CC 1 and CC 0

(condition code) bits of the status word to determine the relationship of a result to 0.

Description

Status Bit Instructions

1 2 ... 223 224 225 226 227 228 229 230 231 232 233 ... 317 318

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