II - DCE FEL ČVUT v Praze

Influence of
supply voltage and
operating status
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
The input values of the SM 321; DI 4 x NAMUR are dependent on the supply
voltages and operating status of the CPU.
Table 2-7 provides an overview of these dependencies.
Table 2-7 Dependencies of the input values for CPU operating status and supply
voltage L+ of SM 321; DI 4 x NAMUR
Operating status
CPU
Supply voltage L+ at
digital module
Input value of digital
module
POWER ON RUN L+ applied Process value
L+ not applied 0-signal
STOP L+ applied Process value
L+ not applied 0-signal
POWER OFF - L+ applied -
SIMATIC S7 Ex Digital Modules
L+ not applied -
Failure of the supply voltage L+ of the SM 321; DI 4 x NAMUR is always
indicated by the SF-LED on the front of the module and additionally entered
in diagnostics.
In the event of the module supply voltage L+ failing, the input value is
initially held for 20 to 40 ms before the ”0” signal is transferred to the CPU.
Dips in the supply voltage of < 20 ms do not change the process value, but
they trigger a diagnostic interrupt and the group error LED is lit.
2-13