Specifications

5
Memory concept
All S7-400 CPUs have two types of
memory: load memory and main mem-
ory.
This splitting of the main memory im-
proves performance by around 100 %.
While a standard processor accesses its
RAM memory at least twice, the special
S7-400 processor accesses the code
memory and the data memory simulta-
neously in a single cycle. This is made
possible by the separate code and data
bus. This is direct performance which is
of benefit to the customer!
The size of the main memory is deter-
mined by selecting the appropriate CPU
from the finely graded range of CPUs. In
the CPU 417, the main memory can be
expanded to up to 20 MB by slotting in
extra memory modules.
The integrated memory (RAM) is ade-
quate for small to medium-sized pro-
grams. For larger programs, the memo-
ry can be increased by slotting in extra
RAM. Additional plug-in flash memory
cards are available to enable retentive
memory without the use of a battery.
The S7-400, as the most powerful PLC in
the SIMATIC controller family, offers im-
portant new system functions when
used with the new operating system 3.1
and in conjunction with other TIA com-
ponents:
Isochrone mode
The S7-400 is now capable of providing
distributed I/O solutions with the capa-
bility to handle extremely fast processes
with very high precision. Consequently,
production can be enhanced while at
the same time increasing quality.
This was made possible by the new sys-
tem function denoted „isochrone
mode“. Isochrone mode means that the
distributed I/O devices obtain signal in-
puts and outputs synchronously
through the equidistant PROFIBUS and
forward these signals for synchronous
processing in the PLC. This way, all input
signals are read, processed synchro-
nously, and in concert with the output
signals. Process response times are
therefore reproducible and defined, and
you can be assured that the distributed
I/O system will process signals synchro-
nously and at the same time.
The precise reproducibility of all pro-
cesses, even very fast ones, is no longer
a problem. Many components now sup-
port isochrone mode, enabling the user
to handle many applications in the area
of motion control, measurement tech-
nology and loop control.
Hardware configuration changes in RUN
(Configuration in RUN, CiR)
Another new feature is that SIMATIC
S7-400 now allows hardware reconfigu-
rations without any adverse effects
while in run mode, e.g. to implement
new sensors or actuators. CiR - Configu-
ration in RUN - reduces time needed for
commissioning and retrofit because
these changes can now be undertaken
while the plant is in full operation. Also,
this new system function makes it pos-
sible for technicians to respond to pro-
cess changes and implement process
optimizations very easily since the plant
must not be re-initialized and synchro-
nized when hardware is changed.
It is possible to add and remove distrib-
uted I/O stations (PROFIBUS DP and
PROFIBUS PA slaves), to add and remove
individual I/O modules in the I/O system
ET 200M, and to assign new parameters
(e.g. to select other interrupt
thresholds).
Memory concept, isochrone mode,
configuration changes in RUN (CiR)
Isochrone mode: Securely handles fast processes
Memory types for the SIMATIC S7-400
External load
memory
· battery-backed
RAM or retentive
Flash Memory
Integrated load
memory
· battery-backed
RAM
Main memory, code
· 50 % for program
· non-backed RAM
Main memory, data
· 50 % for data
· battery-backed RAM
Load memory
· for project data
(blocks,
symbols,
comments,
configuration,
parameteriza-
tion data, etc.)
· customer files
Main memory
· for process-
related mod-
ules, process
image, local
data