Siemens simatic s7-400 FM 450-1, User Manual, Page: 68 / 130

Modes, settings, parameters and commands
8.12 Initiating a process interrupt
Counter module FM 450-1
68
Manual, 02/2014, A5E03648739-02
8.3 Basics on calling modes, settings and commands
Calling modes, settings and commands
● You select modes and settings in the FM°450-1 parameter assignment screen forms.
The parameter assignment data are automatically stored on the programming device and
in the rack SDB.
Notes on installing parameter assignment screen forms and on assigning the FM°450-1
parameters can be found in the chapter "Parameter assignment (Page 41)" and, after the
software has been installed, also in the integrated Help function.
● Modes and settings are modified in the parameter assignment screen forms. The new
mode or setting is valid from the next time the FM 450-1 starts.
● Commands are either generated via hardware signals, which are connected to the front
connector, or by setting the relevant input parameters of the FC CNT_CTRL in the user
program to influence the count process. The input parameters are stored as control bits in
the DB of the FC CNT_CTRL.
Control and status bits in the DB
In addition to the control bits, there are status bits in the DB which signalize the status of the
count process. The control and status bits are each allocated two bytes in the DB (see the
chapter "Assignment of the DB (Page 103)".)
Transferring control and status bits
You transfer control and status bits between the CPU and module with the FC°CNT_CTRL,
which you must integrate into your user program:
Use symbolic names for the control and status bits in the user program. The symbolic names
are used in this chapter in the description of the FC.
The exact description of the FC CNT_CTRL is to be found in the chapter "Program
(Page 45)"; the DB assignments are to be found in the chapter "Assignment of the DB
(Page 103)".