This test function returns the condition of a selected operand (inputs, outputs, flags, data
word, counters or timers) at the end of program execution. This information is obtained
from the corresponding area of the selected operands. During the controlling of variables
respectively in operating mode STOP the input area is directly read. Otherwise only the
process image of the selected operands is displayed.
n
Control of outputs
–
Serves to check the wiring and proper operation of output modules.
–
If the CPU is in RUN mode, so only outputs can be controlled , which are not con-
trolled by the user program. Otherwise values would be instantly overwritten.
–
If the CPU is in STOP - even without user program, so you need to disable the
command output lock BASP (
‘Enable PO’
). Then you can control the outputs
arbitrarily
n
Controlling variables
–
The following variables may be modified: I, Q, M, T, C and D.
–
The process image of binary and digital operands is modified independently of the
operating mode of the CPU.
–
When the operating mode is RUN the program is executed with the modified
process variable. When the program continues they may, however, be modified
again without notification.
n
Forcing variables
–
You can pre-set individual variables of a user program with fixed values so that
they can not be changed or overwritten by the user program of the CPU.
–
By pre-setting of variables with fixed values, you can set certain situations for
your user program and thus test the programmed functions.
CAUTION!
Please consider that controlling of output values represents a potentially
dangerous condition.
Even after a power cycle forced variables remain forced with its value,
until the force function is disabled.
These functions should only be used for test purposes respectively for
troubleshooting. More information about the usage of these functions
may be found in the manual of your configuration tool.
‘PLC
è
Monitor/Modify
Variables’
System 300S
+
Deployment CPU 315-4PN23
Control and monitoring of variables with test functions
HB140 | CPU | 315-4PN23 | en | 18-02
74
