Technical data

➣
In the bus cycle, GP bytes are only received when the data have
changed on the sender.
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In the PLC, the control program evaluates the received input byte
(PY 1).
The value of the GP byte at the time the control program accesses it in the
PLC is decisive. If data is received several times between two accesses by
the PLC, only the current value is passed on to the control program. All
intermediate values are lost.
Essential features of the FREE mode:
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Minimum cycle load (corresponds to the cycle load that would occur
simply by plugging in the corresponding input/output modules.
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Minimum load on the CP 5430 TF/CP 5431 FMS.
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Simple programming (single handling block call; HDB SYNCHRON
during start-up).
☞
If GP bytes need to be transferred together because they form
a logical unit (e.g. a control parameter requiring a word), the
FREE update mode must under no circumstances be
selected. With this mode, there is no guarantee that the GP
bytes which belong together are actually transferred together.
The receiver would then process inconsistent values.
Communication with Global I/Os B8976060/01
Volume 1 9 - 10