Siemens SIMATIC S7-400H - Effects of Link-up and Update

Linking and Synchronizing
6-2
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
6.1 Effects of Link-up and Update
Link-up and update are indicated by the REDF LEDs on the two CPUs. On link-up
these LEDs flash with a frequency of 0.5 Hz, and on update with a frequency of
2 Hz.
Link-up and update have various effects on the execution of the user program and
the communication functions.
Table 6-1 Properties of link-up and update
Process
Linking Update
Execution of the user
program
All priority classes (OBs)
are executed.
Execution of the priority classes
is delayed by sections. All the
requirements are caught up with
after the update.
You will find the details in the
sections which follow.
Deletion, loading,
generation and
compression of blocks
Blocks cannot be deleted,
loaded, generated or
compressed.
If these actions are being
executed, link-up and
update will not be possible.
Blocks cannot be deleted,
loaded, generated or
compressed.
Execution of
communication
functions, PG operation
Communication functions
are being executed.
Execution of the functions is
restricted and delayed by
sections. All the delayed
functions are caught up with after
the update.
You will find the details in the
chapters which follow.
CPU self-test Will not be performed Will not be performed
Test and commissioning
functions, such as
“Monitor and Control
Tag”, “Monitor (On/Off)”
No test and commissioning
functions are possible.
If these actions are being
executed, link-up and
update will not be possible.
No test and commissioning
functions are possible.
Processing of the
connections to the
master CPU
All the connections remain;
no new connections can be
made.
All the connections remain; no
new connections can be made.
Broken connections will only be
re-made after the update
Processing of the
connections to the
standby CPU
All the connections are
broken; no new
connections can be made.
All the connections are already
broken. They are aborted on
link-up.