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
Summary of Contents for CPU 948
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Page 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Page 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Page 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...