Downloading In Run Mode - Siemens S7-1200 System Manual

Startup
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14.12

Downloading in RUN mode

The CPU supports "Download in RUN mode". This capability is intended to allow you to
make small changes to a user program with minimal disturbance to the process being
controlled by the program. However, implementing this capability also allows massive
program changes that could be disruptive or even dangerous.
Risks with downloading in RUN mode
When you download changes to the CPU in RUN mode, the changes immediately affect
process operation. Changing the program in RUN mode can result in unexpected system
operation, which could cause death or serious injury to personnel, and/or damage to
equipment.
Only authorized personnel who understand the effects of RUN mode changes on system
operation should perform a download in RUN mode.
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
The clearing of the I memory area is not
affected by the Force function.
The initialization of the outputs values is
not affected by the Force function.
During the execution of the startup OBs,
the CPU applies the force value when
the user program accesses the physical
input.
The storing of interrupt events into the
queue is not affected.
The enabling of the writing to the
outputs is not affected.
WARNING
Online and diagnostic tools
14.12 Downloading in RUN mode
RUN
①
While writing Q memory to the physical
outputs, the CPU applies the force value as
the outputs are updated.
②
When reading the physical inputs, the CPU
applies the force values just prior to copying
the inputs into I memory.
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 or writes the physical
output.
④
Handling of communication requests and self-
test diagnostics are not affected by the Force
function.
⑤
The processing of interrupts during any part of
the scan cycle is not affected.
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