Siemens CPU 314 Reference Manual

CPUs
1-21
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
Forcing with the CPU 312 IFM to 316-2 DP:
!
Caution
Forced values in the input process image can be overwritten by write instructions
(e.g. T EB x, = E x.y, copying with SFC etc.) and peripheral read instructions (e.g.
L PEW x) in the user program, as well as by write instructions of PG/OP opera-
tions!
Outputs initialized with forced values only return the forced value if the user pro-
gram does not execute any write accesses to the outputs using peripheral write
commands (e.g. TPQB x ) and if no PG/OP functions write to these outputs!
Always note that forced values in the I/O process image cannot be overwritten by
the user program or PG/OP functions!
Execute force
job for outputs
With S7-300 CPUs, forcing is the same as “cyclical modify”
PII
transfer
User program
OS
T PQW
Forced value
overwritten by T
PQW!
Execute force
job for inputs
Forced
value
Execute force
job for outputs
Forced
value
Execute force
job for inputs
OS .... Operating system execution
PIO
transfer
PII
transfer
OS
PIO
transfer
Figure 1-4 The Principle of Forcing with S7-300 CPUs (CPU 312IFM to 316-2DP)

Siemens CPU 314 Specifications

General

Brand	Siemens
Model	CPU 314
Category	Controller
Language	English