Special Bit Memories And Their Functions - Siemens SINUMERIK 828D Function Manual

P4: PLC for SINUMERIK 828D
14.3 Programming
• If you only want to load the actual values of a data block from the target system, then first open the
corresponding project in the Programming Tool PLC828 or load it from the target system. You can now load
the actual values. You cannot load the data block if the structure of the data block in the target system does
not match that of the data block of the project that has been opened, or if the project that has been opened
does not have a data block.
14.3.2.7

Special bit memories and their functions

Special bit memories SMB0 (SM0.0 ... SM0.6) include seven bits that are updated by the PLC firmware at the
end of each cycle. You can realize various functions in your program.
Special bit memories
(write protected)
SM0.0
SM0.1
SM0.2
SM0.3
SM0.4
SM0.5
1118
Description
This bit is always switched on.
This bit is switched on in the first cycle. It is used, for example, to call an
initialization subprogram.
This bit is switched on for the length of a cycle, if retentive data has been
lost. It can be used either as an error bit memory or as a mechanism for
calling up special startup sequences.
This bit is switched on for the length of a cycle if the RUN operating mode
has been set after switching on (power on). This permits a warm-up time for
the system before starting operation.
This bit ensures a cycle that is switched-on for 30 seconds and switched-out
30 seconds. And more precisely for a cycle time of 1 minute. This way you
have an easy to program delay or a cycle time of 1 minute.
This bit ensures a cycle that is switched-on for 0.5 seconds and switched-out
for 0.5 seconds. And more precisely for a cycle time of 1 second. This means
that you have an easy way of programming a delay time or a cycle time of 1
second.
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
Basic Functions