Process Image Update Of The Cpus; Cpu-Specific Factors For The User Program Processing Time; Updating The S7 Timers - Siemens SIMATIC S7-300 Series Reference Manual

Table 3-2

Process image update of the CPUs

Components
K Base load
A For each byte in rack
"0"
B For each byte in racks
"1 to 3"
D For each byte in DP
area for integrated DP
interface
User Program Processing Time:
The user program processing time is made up of the sum of the execution times
for the instructions and the SFB/SFCs called up. These execution times can be
found in the Instruction List. Additionally, you must multiply the user program
processing time by a CPU-specific factor. This factor is listed in Table 3-3 for the
individual CPUs.
Table 3-3

CPU-specific Factors for the User Program Processing Time

Se- CPU 312 CPU 313
quence IFM
Factor 1.23 1.19
S7 timers
In the case of the CPU 318-2, the updating of the S7 timers does not extend the
cycle time.
The S7 Timer is updated every 10 ms.
You can find out in Section 3.3 how to include the S7 timers in calculations of the
cycle and response times.
Table 3-4

Updating the S7 Timers

Sequence 312 IFM
Updating the S7 Number of
timers (every 10 ms) simultaneously
active S7
timers
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
CPU CPU CPU
312 313 314
IFM
162ms 142ms 142ms
14.5ms 13.3ms 13.3ms
16.5ms 15.3ms 15.3ms
– – –
CPU 314 CPU 314
IFM
1.15 1.15
313 314
Number of simultaneously active S7 timers
10 ms
Cycle and Reaction times
CPU CPU CPU
314 315 315-2
IFM DP
147ms 109ms 10ms
13.6ms 10.6ms 20ms
(per
word)
15.6ms 12.6ms 22ms
(per
word)
– – 12ms
(per
word)
CPU 315 CPU
CPU
316-2 DP
315-2DP
1.15 1.19 1.19
314 IFM 315
315-2DP
8 ms
CPU CPU
316-2 318-2
DP
10ms 20ms
6 ms
20ms
(per
word)
22ms 12.4ms
(per
word)
12ms 1ms
(per
word)
CPU
318-2
1.0
316-2DP
3-7