Addresses

CAUTION

If you use pointers to addresses, then the contents of addresses can be moved during an online change. If you use absolute addresses, then the contents of addresses does not change during an online change.

Syntax:

% <memory area number> <size prefix> <position number> .<bit position number>

% <address>	Required Address in the memory area % <memory area prefix> <size prefix> <memory position>
<memory area prefix>	Required I: Input memory area Memory area for input signals and inputs For physical inputs via input drivers and sensors Q: Output memory area Memory area for output signals and outputs For physical outputs via output drivers and actuators M: Flag memory area
<size prefix>	Optional No size prefix: bit Single bit X: Bit Single bit B: Byte 8-bit data width W: Word 16-bit data width D: Dword 32-bit data width
<memory position>	<position number> . <bit position number> Example: %IB2.4 stands for the 5th bit of the 3rd byte
<position number>	Required The numbering depends on the target system and starts at 0.
. <bit position number>	Optional 0..7 for one byte

When defining an address, you use specific strings to express the memory position and size. An address comprises the percent sign (%), followed by the memory area prefix, the optional size prefix, and the memory area position. The numbering which you use for addressing the memory position depends on the target system.

Examples

%QX7.5 %Q7.5	Single bit address of the output bit 7.5
%IW215	Word address of the input word 215
%QB7	Byte address of the output byte 7
%MD48	Address of a double word at memory position 48 in flag memory
%IW2.5.7.1	Word address of an input word; interpretation dependent on the current controller configuration
VAR wVar AT %IW0 : WORD; END_VAR	Variable declaration with address information of an input word
VAR xActuator AT %QW0 : BOOL; END_VAR	Boolean variable declaration Note: In the case of Boolean variables, one byte is allocated internally when a single bit address is not specified. A change in the value of xActuator affects the range from QX0.0 to QX0.7.
VAR xSensor AT %IX7.5 : BOOL; END_VAR	Boolean variable declaration with explicit specification of a single bit address When accessed, only the input bit 7.5 is read.

Memory position