9.1 Introduction
The STEP 5 programming language contains operations with which
you can access the entire memory area. These operations belong to the
"system operations".
The operations described in this chapter work with 20-bit absolute
addresses. Consequently, they are dependent on the memory size and
type, the peripherals, CPs, and IPs of your programmable controller.
Warning
If the operations described in this chapter are not used properly,
STEP 5 blocks and system data can be overwritten. Therefore,
only experienced programmers should use operations that work
with absolute addresses.
Local memory
Local memory is the memory area that is available in each CPU. It
includes the following: user submodule, RI/RJ area, RS/RT area,
counters, timers, flags, process images.
Global memory
Global memory exists only once for all CPUs. You address it via the
S5 bus.
Memory organization
Memory areas are organized in bytes or in words as follows:
•• Bytes: Each address addresses a byte.
•• Words: Each address addresses a 16-bit word
(= 2 bytes).
Organization of the local memory is fixed (see Chapter 8)
Organization of the global memory depends on the type of modules
that are plugged into the programmable controller:
Introduction
CPU 948 Programming Guide
9 - 4 C79000-G8576-C848-04
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