Siemens CPU 948, Programming Manual

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7.4 Examples of Parameter Assignment
7.4.1
STEP 5 Programming
Example A:
You want to use three CPUs in the multiprocessor mode: CPU A, B and C. CPU
A and B work closely with each other, often exchange data and execute a
complicated start-up program.
CPU C executes a short, time-critical program largely independent of A and
B.
As standard, all CPUs operating in the multiprocessor mode start cyclic
program execution together, i.e. the CPUs wait for each other until they
have all completed their start-up and then change to cyclic program
execution together.
Since CPU C executes its program independently of the other CPUs and has a
very short start-up program
, there is no need to synchronize its start-up
with the others. By assigning parameters in DX 0, CPU C can start its
cyclic program immediately after completing the start-up without waiting
for CPU A and B.
The parameter for synchronizing the CPUs in the multiprocessor mode is the
second parameter in the first field. To maintain the order of the
parameters, the first parameter for the start up must have the default
value (AUTOMATIC WARM RESTART after POWER UP).
Program DX 0 for CPU C as follows:
DX 0 Start ID "MASKX0" DW 0: KH = 4D41
DW 1: KH = 534B
DW 2: KH = 5830
1st field ID/length DW 3: KH = 0202
Parameter 1 DW 4: KH = 1000
Parameter 2 DW 4: KH = 2001
End ID DW 5: KH = EEEE
Once you have loaded this DX 0 in the program memory, it becomes effective
at the next COLD RESTART. Since CPU C runs through a very short start-up
program and does not wait for A and B, its green RUN LED lights up
immediately following start-up. The BASP signal (disable command output)
is, however, only deactivated when all three CPUs have completed their
start-up. This means that CPU C cannot access the digital I/Os.
Examples of Parameter Assignment
CPU 948 Programming Guide
7 - 12
C79000-G8576-C848-04