Technical data

Both in the cold restart branch (OB 20) and in the warm restart branch (OB
21/22) each CP interface to be used later must be synchronized
(SYNCHRON HDB). From the cold restart branch, the PLC operating
system branches directly to the first cycle checkpoint. The process image of
the inputs (PII) is read in for the first time at this point. The first RECEIVE
synchronization point for the CP 5430 TF is therefore already in the cold
restart branch.
After the warm restart (OB21/22) the PLC cycle is resumed at the point at
which it was interrupted. The old PII is still valid for the remainder of the
PLC cycle and is only updated at the next PLC cycle checkpoint. If a check
of the ZP image is required with a warm restart, the control HDB should be
called in a loop at the end of OB21/22 until the status word contains no
further relevant error bits.
Cyclic operation
The cyclic program has the following structure for all stations in the CYCLE
SYNCHRONIZED update mode:
Control program
Cycle
checkpoint
HDB RECEIVE call with
ANR 211
(last statement in cyclic
program before the end
of the block)
Call HDB SEND with
ANR 210
(at the start of the cyclic
program)
Fig. 10.7: Structure of the Cyclic Program
Communication with Cyclic I/Os B8976060/02
Volume 1 10 - 14