Siemens S7-300 - 8.7 SM 326; F-DO 10 x DC 24 V;2 A PP (6 ES7326-2 BF10-0 AB0)

7HVWLQJIXQFWLRQVDQG'LDJQRVWLFV
S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01
11-3
PIQ
transfer
Execute force
job for inputs
Execute force
job for inputs
T PQW
Besy
PII
transfer
User program
Forced value
Forced value
overwritten by
T PQW!
With S7-300 CPUs, forcing is the same as "cyclical modify"
OS: operating system execution
PIQ
transfer
Besy
PII
transfer
Forced value
Execute force
job for outputs
Execute force
job for outputs
Figure 11-1 Principle of Forcing with S7-300 CPUs (all CPUs except 318-2 DP)
7KHGLIIHUHQFHVEHWZHHQIRUFLQJDQGFRQWUROOLQJYDULDEOHV
Table 11-1 The differences between forcing and controlling variables
&KDUDFWHULVWLFV)XQFWLRQ )RUFLQJZLWK
&38'3
DQG6
)RUFLQJZLWK
6
ZLWKRXW
'3
&RQWUROOLQJ
9DULDEOHV
Memory bit (M) Yes - Yes
Timers and counters (T, C) - - Yes
Data Blocks (DB) - - Yes
Inputs and outputs (I, Q) Yes Yes Yes
Peripheral Inputs (PI) Yes - -
Peripheral Outputs (PO) Yes - Yes
User program can overwrite
modify/force values
- Yes Yes
Maximum number of force
values
256 10 -
&URVVUHIHUHQFH
Details on test functions of the software are found in the 67(32QOLQH+HOS and
in the 67(33URJUDPPLQJ0DQXDO.