Startup Operating Mode; Link-Up And Update Operating Modes - Siemens SIMATIC S7-400H Manual

System and Operating Modes of the S7-400H
4.3.2

STARTUP Operating Mode

Except for the additions described below, the CPUs of the S7-400H behave in
exactly the same way in the STARTUP mode as the standard CPUs on the S7-400
do.
Types of startup
CPU 417-4H distinguishes between a cold restart and a complete restart (warm
restart).
Hot restart is not supported by CPU 417-4H.
Startup processing by the master CPU
The startup system mode of an S7-400H is processed entirely by the master CPU;
the standby CPU plays no part in startup.
At STARTUP the master CPU compares the existing I/O configuration with the
hardware configuration that you created with STEP 7. If there are differences, the
master CPU reacts in the same way a standard CPU would on the S7-400.
The master CPU checks and assigns parameters to the
1. switched I/O
2. one-sided, single-channel I/O.
Further information
You will find detailed information on the STARTUP mode in the Programming with
STEP 7 manual.
4.3.3

LINK-UP and UPDATE Operating Modes

Before the fault-tolerant system accepts the Redundant system mode the master
CPU checks and updates the memory contents of the standby CPU. (Exception: in
the case of link-up and update with subsequent switch-over to CPU with modified
configuration).
Checking and updating of the memory contents are performed in two phases which
run consecutively and will be referred to in the following as "link-up" and "update".
During link-up and update the master CPU is always at RUN and the standby CPU
is in LINK-UP or UPDATE mode.
When executing a link-up and update a distinction is made between whether the
Redundant system mode or a master/standby switch-over is to be achieved (for
master/standby switch-over for configuration modifications see Chapter 10).
Detailed information on the link-up and update process can be found in section 5.2
4-8
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04