User Manual

PLC concepts made easy

4.4 Memory areas, addressing and data types

Easy Book

Manual, 03/2014, A5E02486774-AF

Note

Valid data types that can be accessed by slice are Byte, Char, Conn_Any, Date, DInt,

DWord, Event_Any, Event_Att, Hw_Any, Hw_Device, HW_Interface, Hw_Io, Hw_Pwm,

Hw_Sub

Module, Int, OB_Any, OB_Att, OB_Cyclic, OB_Delay, OB_WHINT, OB_PCYCLE,

OB_STARTUP, OB_TIMEERROR, OB_Tod, Port, Rtm, SInt, Time, Time_Of_Day, UDInt,

UInt, USInt, and Word. PLC Tags of type Real can be accessed by slice, but data block tags

of type Real cann

ot.

Examples

In the PLC tag table, "DW" is a declared tag of type DWORD. The examples show bit, byte,

and word slice access:

LAD

FBD

SCL

Bit access

IF "DW".x11 THEN

...

END_IF;

Byte access

IF "DW".b2 = "DW".b3

THEN

...

END_IF;

Word access

out:= "DW".w0 AND

"DW".w1;

4.4.4

Accessing a tag with an AT overlay

The AT tag overlay allows you to access an already-declared tag of a standard access block

with an overlaid declaration of a different data type. You can, for example, address the

individual bits of a tag of a Byte, Word, or DWord data type with an Array of Bool.