8. How easyE4 works internally
8.1 Program execution
8. How easyE4 works internally
8.1 Program execution
When using the LD or FBD programming language, the program will be executed as
follows:
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The program will start by reading the hardware's input states and writing them to
the image table register. After this, it will run through network 01 in its entirety
and not only process all function blocks and logic circuitry, but also write the
state of all mapping assignments (Q, M, etc., and function blocks) to the image
table register. It will then run through the next network (if any networks are
jumped over, they will not be run through). Once the last network has been run
through, the resulting output states will be transmitted to the hardware The cycle
will then start again.
In the Programming language ST
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The program will start by reading the hardware's input states and writing them to
the image table register. After this, it will execute the statement and instruction
list from top to bottom and modify the image table register every time there is a
mapping assignment (if any statements or instructions are jumped over, they will
not be executed). The cycle will then start again.
When using the EDP (easy Device Programming) programming language
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This programming language is the same one that can be use for programming dir-
ectly on the base device. The way in which this program will be executed is
identical to the way programs are executed on the existing easy500, easy700, and
easy800 devices.
In conventional control systems, a relay or contactor control processes all the rungs
in parallel. The speed with which a contactor switches is thus dependent on the com-
ponents used, and ranges from 15 to 40 ms for relay pick-up and drop-out.
easyE402/24 MN050009ENEaton.com
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