Different Cycle Times - Siemens Simatic S7-300 Technical Data Manual

Cycle and reaction times
5.2 Cycle time
Extension of the cycle time due to error
Table 5-8
Type of error
312C
313C
313C2
314C-2
312
314
315
317
The interrupt OB processing time must be added to this extended time. The times required
for multiple nested interrupt/error OBs are added accordingly.
5.2.3

Different cycle times

Overview
The cycle time (T
cycle times T
interrupted by a time-of-day interrupt OB (here: OB 10).
Updating
PIO
Block processing times may fluctuate
Fluctuation of the block processing time (e.g. OB 1) may also be a factor causing cycle time
fluctuation, due to:
• conditional instructions,
• conditional block calls,
• different program paths,
• loops etc.
5-8
Cycle time extension as a result of errors
Programming errors
600 μs
400 μs
400 μs
400 μs
600 μs
400 μs
400 μs
100 μs
) length is not the same in every cycle. The figure below shows different
cyc
and T . T
cyc1 cyc2 cyc2
Current cycle
T
cyc 1
Updating
PII OB1 CCP
is longer than T , because the cyclically executed OB1 is
cyc1
Next cycle
T
cyc 2
OB10
Updating
Updating
PIO PII
OB1
I/O access errors
600 μs
400 μs
400 μs
400 μs
600 μs
400 μs
400 μs
100 μs
Cycle after next
Updating Updating
CCP PIO PII
OB1
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05