Siemens CPU 315-2 DP Hardware And Installation Guide

7HVWLQJ)XQFWLRQV'LDJQRVWLFVDQG)DXOW(OLPLQDWLRQ
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
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 in S7-300 CPUs
7KHGLIIHUHQFHVEHWZHHQIRUFLQJDQGPRGLI\LQJYDULDEOHV
Table 11-1 The differences between forcing and modifying variables
&KDUDFWHULVWLFVIXQFWLRQ )RUFLQJ 0RGLI\LQJ9DULDEOHV
Memory bit (M) - Yes
Timers and counters (T, C) - Yes
Data Blocks (DB) - Yes
Inputs and outputs (I, Q) Yes Yes
Peripheral Inputs (PI) - -
Peripheral Outputs (PO) - Yes
User program can overwrite modify/force
values
Yes Yes
Maximum number of force values 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.

Siemens CPU 315-2 DP Specifications

General

Brand	Siemens
Model	CPU 315-2 DP
Category	Controller
Language	English