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Glossary-7

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

C79000-G7076-C504-02

The OR bit is needed if you perform a logical AND before OR operation.

The OR bit shows these instructions that a previously executed AND function

has supplied the value 1, thus forestalling the result of the logical OR

operation. Any other bit-processing command resets the OR bit.

The status bit OS stands for overflow. An overflow can occur, for example,

after a math operation.

You can use a pointer to identify the address of a variable. A pointer contains

an identifier instead of a value. If you allocate an actual parameter type, you

provide the memory address. With STEP 7 you can either enter the pointer in

pointer format or simply as an identifier (e.g. M 50.0). In the following

example, the pointer format is shown with which data from M 50.0 is

accessed:

P#M50.0

A project is a container for all objects in an automation task, irrespective of

the number of stations, modules, and how they are connected in networks.

Reference data are used to check your CPU program and include cross

reference lists, assignment list, user program structure, the list of unused

addresses, and the list of addresses without symbols.

A type of addressing in which the address of an instruction indicates

indirectly via an address register and an offset the memory location of the

value with which the instruction is to work.

The result of logic operation (RLO) is the current signal state in the

processor, which is used to process other binary signals. The execution of

certain instructions depends entirely on their preceding RLO.

OR Bit

Overflow Bit

Pointer

Project

Reference Data

Addressing

Result of Logic

Operation (RLO)

Glossary

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Siemens NAN 67 Series Wartungshandbuch Seite 301