Initialise to random values

profibusdp · Jan 31, 2007

Hi all,

Breaking my head on this one:
PLC: Siemens s7300
Programming language: STL/LAD
Q: Initialise an array of 100 data words with random values

Notes: 1) Hopefully can be done in 1 step (initialise)
2) DataBlock or Array or Table? Any will do...

dchartier · Feb 1, 2007

Hello profibusdp;

If the question is : how to automate the initialization of an array of 100 words (you know of course that you can assign manually an initial value to any variable...):

-start by declaring your array, in a DB for example;

-create a loop (search this forum for indexed addressing, indirect addressing, you will find many good snippets of code in STL)

-in this loop, generate a random number (see below), store it in the first available un-initialized member of the array, then increment the pointer to the next member, and repeat until you have reached the ebnd of the array.

For the generation of a random number, here is a suggestion from Siemens' support website:

calculation of a random number with STEP 7

QUESTION:
How can you calculate random numbers between 0 and a specified upper limit?

ANSWER:
You can use the system function SFC64 "TIME_TCK" to generate a random number. From the system time you create the absolute value and then run an integer division with the upper limit as divisor. Determine the remainder left by this division operation. You can use this number as random number.

Hope this helps,

Daniel Chartier

L D[AR2P#0.0] · Feb 1, 2007

Why do the values have to be random, what processing will be done on the values ?

PLucas · Feb 1, 2007

L D[AR2 said:
Why do the values have to be random,

Because that's what the tutor asked for?

Paul

rdrast · Feb 1, 2007

This assignment has been given before. Try searching "Random" on this site.

Initialise to random values

profibusdp

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dchartier

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L D[AR2P#0.0]

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PLucas

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rdrast

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