User Manual

PLC concepts made easy
4.4 Memory areas, addressing and data types
Easy Book
64 Manual, 03/2014, A5E02486774-AF
Configuring the I/O in the CPU and I/O modules
When you add a CPU and I/O modules to your
configuration screen, I and Q addresses are
automatically assigned. You can change the
default addressing by selecting the address field in
the device configuration and typing new
numbers.
•
Digital inputs and outputs are assigned in
groups of 8 points (1 byte), whether the module
uses all the points or not.
•
Analog inputs and outputs are assigned in
groups of 2 points (4 bytes).
The figure shows an example of a CPU 1214C with two SMs and one SB. In this example,
you could change the address of the DI8 module to 2 instead of 8. The tool assists you by
changing address ranges that are the wrong size or conflict with other addresses.
4.4.3
Accessing a "slice" of a tagged data type
PLC tags and data block tags can be accessed at the bit, byte, or word level depending on
their size. The syntax for accessing such a data slice is as follows:
● "<PLC tag name>".xn (bit access)
● "<PLC tag name>".bn (byte access)
● "<PLC tag name>".wn (word access)
● "<Data block name>".<tag name>.xn (bit access)
● "<Data block name>".<tag name>.bn (byte access)
● "<Data block name>".<tag name>.wn (word access)
A double word-sized tag can be accessed by bits 0 - 31, bytes 0 - 3, or word 0 - 1. A word-
sized tag can be accessed by bits 0 - 15, bytes 0 - 1, or word 0. A byte-sized tag can be
accessed by bits 0 - 7, or byte 0. Bit, byte, and word slices can be used anywhere that bits,
bytes, or words are expected operands.