Online functionality
8.7 Forcing variables in the CPU
Easy Book
96
Manual, 05/2009, A5E02486774-01
When an input or output is forced in a watch table, the force actions become part of the user
program. If you close STEP 7 Basic, the forced elements remain active for the user program
being executed by the CPU program until they are cleared. To clear these forced elements,
You must use STEP 7 Basic to connect with the online CPU and use the watch table to turn
off or stop the force function for those elements. If the CPU is executing the user program
from a write-protected memory card, you cannot initiate or change the forcing of I/O from a
watch table because you cannot override the values in the write-protected user program.
Any attempt to force the write-protected values generates an error.
If you use a memory card to transfer a user program, any forced elements on that memory
card will be transferred to the CPU.
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Startup
RUN
A
The clearing of the I memory area is not
affected by the Force function.
① While writing Q memory to the physical
outputs, the CPU applies the force value as
the outputs are updated.
B
The initialization of the outputs values is
not affected by the Force function.
② After copying the state of the physical inputs
to I memory, the CPU applies the force
values.
C
During the execution of the startup OBs,
the CPU applies the force value when
the user program accesses the physical
input.
③ During the execution of the user program
(program cycle OBs), the CPU applies the
force value when the user program accesses
the physical input.
D
After copying the state of the physical
inputs to I memory, the CPU applies the
force values.
④ Handling of communication requests and self-
test diagnostics are not affected by the Force
function.
E
The storing of interrupt events into the
queue is not affected.
⑤ The processing of interrupts during any part of
the scan cycle is not affected.
F
The enabling of the writing to the
outputs is not affected.
