SIMATIC S7- 400 CPUs
CPUs for demanding tasks
There is a graded range of CPUs from the entry-level CPU right
up to the high-performance CPU for configuring the controller.
All CPUs control large quantity structures; several CPUs can
work together in a multicomputing configuration to boost performance.
Thanks to their high processing speed and deterministic
response times, the CPUs enable short machine cycle
times. |
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The different CPUs are distinguished by, for example, RAM, address
range, number of connections and execution time.
As
well as the standard CPUs, there are also two fail-safe and two
fault-tolerant CPUs available. 3 CPUs with integrated PROFINET
interface are now part of the CPU range.
Performance
The S7-400 is characterized not only by short response times,
but also by large performance reserves. Extremely short response
times can be achieved in this way even when simultaneous
communication is required or other unforeseen loads
occur. This makes specified response times possible, for example
the response time of an output signal to a change in an input
signal.
Additional functions can also be integrated without any further
hardware investment. Examples of new functions include
the saving and processing of quality data, user-friendly diagnostics
or vertical integration into higher-level MES solutions.
The improved communication performance enables highspeed
communication over Industrial Ethernet as well as efficient
connection of the field level via PROFIBUS, for example
with isochronous tasks.
Multicomputing
Multicomputing, that is, the simultaneous operation of several
CPUs in one S7-400 central controller, offers users different
benefits:
- The overall performance of an S7-400 can be shared by
means of multicomputing. For example, complex tasks in
technologies such as open-loop control, computing or
communication can be split and assigned to different CPUs.
Each CPU is assigned its own, local I/O for this purpose.
- Some tasks can also be disconnected from each other in
multicomputing, that is, one CPU processes the time-critical
process tasks and another handles the non-time-critical
tasks.
In multicomputing operation, all CPUs behave like a single
CPU, that is, when one CPU goes to STOP, the others are also
halted. The actions of several CPUs can be coordinated selectively
by instruction via synchronization calls. In addition, data exchange between the CPUs takes place at an
extremely high speed via the "global data" mechanism.
Data/program memory
All CPUs of the S7-400 have a separation between data memory
and program memory. This division of the work memory
provides a performance boost of 100% in some constellations.
Whereas a standard processor has to access its RAM at least
twice, the S7-400 special processor accesses the code memory
and data memory simultaneously in the same cycle. There are
also separate code and data buses for this purpose. This provides
the user with additional performance power!
The size of the work memory is determined CPU that can be selected
from a finely graded range of CPUs.
The integral load memory (RAM) is sufficient for small to medium-
sized programs. For larger programs, the load memory is
enlarged by plugging in RAM or FEPROM memory cards (64 KB
to 64 MB).
With the 64 MB RAM memory card, it is possible to store the
contents of the entire work memory of even the largest CPU.
This RAM memory is backed up using a battery of the power
supply. RAM memory cards are used especially in cases where,
for example, the user program has to be modified frequently
during the startup phase. RAM memory cards enable faster
saving than FEPROM memory cards, and any number of write
cycles.
For retentive storage without backup battery, there are plug-in
FEPROM memory cards available whose data are retained even
after the card has been disconnected.
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