Direct Addresses

Overview

A direct address specified in EcoStruxure Machine Expert contains the following information:

  • Information on the memory location.

  • Memory format (size)

  • Offset of the memory location. The offset is specified by an integer number, which in case of a bit address is followed by a dot and a number for the position of the bit.

Syntax

%<memory area prefix><size prefix><number|.number|.number....>

The following memory area prefixes are supported:

I

input (physical inputs via input driver, sensors)

Q

output (physical outputs via output driver, actors)

M

memory location

The following size prefixes are supported:

X

single bit

B

byte (8 bits)

W

word (16 bits)

D

double word (32 bits)

Examples

Example address

Description

%QX7.5

output bit 7.5

%Q7.5

%IW215

input word 215

%QB7

output byte 7

%MD48

double word in memory position 48 in the memory location

ivar AT %IW0: WORD;

example of a variable declaration including an address assignment

For further information, refer to the AT Declaration chapter.

NOTE: The memory size for input, output, and memory data (declarations with AT %I, %Q and %M) is predefined by the target device and can be overwritten in the properties of an application object for PacDrive controllers (PacDrive LMC Eco, PacDrive LMC Pro/Pro2).

Byte Addressing Mode and Word Addressing Mode

Devices either use byte addressing mode or word addressing mode.

Examples

Mode

Example

Byte addressing 

ADR(%IW1) = ADR(%IB1)

Word addressing 

ADR(%IW1) = ADR(%IB2)

The range for the second element of the bit address that is the number following the dot, is as follows:

  • byte addressing mode: 0...7

  • word addressing mode: 0...15

Also for the handling of bit addresses, you can configure the devices differently. They are then interpreted correspondingly by the EcoStruxure Machine Expert compiler.

Example: In a byte-addressing device, the bit address %IX2.5 addresses byte 2 (IB2). In a word-addressing device, however, it addresses word 2, which refers to a different location within the memory.

NOTE: Boolean values are allocated bytewise if no explicit single-bit address is specified. Example: A change in the value of varbool1 AT %QB7 affects the range from QX0.0 to QX0.7.