Technical data

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The control program can then work with these values under PY0.
The advantage of the CYCLE-SYNCHRONIZED mode is that the time at
which the ZP is sent or received is fixed in the control program.
To ensure that the ZP input area of the CPU is also updated at a defined
point in time, an HDB RECEIVE with job number 211 must be called in the
control program, normally at the end of the cyclic control program.
To ensure that the ZP output area of the CPU is also updated at a defined
point in time, an HDB SEND with job number 210 must be called in the
control program, normally at the start of the cyclic control program.
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With short PLC cycle times (< 50 ms) the HDB
SEND/RECEIVE calls with job numbers 210/211 may extend
the PLC cycle time. The load on the CP 5430 TF may also
increase so that the transmission times of the global I/Os
deteriorate.
If you have short PLC cycle times, make sure that the time between two
HDB calls is greater than 50 ms (e.g. by programming HDB
SEND/RECEIVE calls with job numbers 210/211 in every nth PLC cycle).
The normal safety philosophy of SIMATIC control systems, resetting all the
output bytes if the PLC stops and clearing the input bytes belonging to an
I/O device if this fails, is also used here. The total number of GP and ZP I/O
bytes processed by the CP must not exceed 256 input or output bytes, but
can be assigned to the P or O areas (O area only with S5 135U, S5 150U
and S5 155U).
Sequence of the data transmission
The start-up OBs have the following task with the cyclic I/Os data
transmission mode;
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They must synchronize the CP 5430 TF interface
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They can make sure that the PLC only starts up when certain or all
stations are ready to transmit and receive (i.e. when there are no ZP
error messages)
Communication with Cyclic I/Os B8976060/02
Volume 1 10 - 12