4.8.3
Behavior of the SM 421; DI 16 x DC 24 V
Effect of operating mode and supply voltage on the input values
The input values of the SM 421; DI 16 x 24 DC depend on the operating mode of the CPU and
on the supply voltage of the module.
Table 4-9
Relationships of the analog input values on the CPU's operating state and on the L+ supply
voltage
CPU operating state
Power supply L+ at digital module
Input value of digital module
POWER ON
RUN
L+ present
Process value
L+ missing
0 signal*
STOP
L+ present
Process value
L+ missing
0 signal*
POWER OFF -
L+ present
-
L+ missing
-
* Depends on the parameter assignment
Reaction to failure of the supply voltage
Failure of the supply voltage of the SM 421; DI 16 x 24 DC is always indicated by the EXTF
LED on the module. This information is also available on the module (entry in diagnostic data.)
Diagnostics interrupt triggering is based on parameter settings.
Short-circuit at the sensor supply Vs
The relevant Vs LED goes dark if a short-circuit is detected at the sensor supply Vs, irrespective
of parameter settings.
Effect of errors and parameter assignment on the input values
The input values of the SM 421; DI 16 x 24 DC are affected by certain errors and the parameter
assignment of the module. The following table lists the effects on the input values.
You can find more diagnostic messages in the Appendix "Diagnostic Data of the Signal
Modules".
Table 4-10
Relationships between the input values of errors and the configuration
Diagnostic message
"Diagnostics"
parameter
"Reaction to Error"
parameter
Input value of digital module
No module parame‐
ters
Cannot be disa‐
bled
Not relevant
0 signal (all channels)
Front connector miss‐
ing
Substitute a value
(SV)
Configured substitute value
KLV
Last read, valid value
Digital modules
4.8 Digital input module SM 421; DI 16 x DC 24 V (6ES7421-7BH01-0AB0)
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
107