Siemens SIMATIC S7-300 Reference Manual page 237

4.5 Behavior of the Analog Modules
Introduction
In this section, you will find information on:
• How the analog input and output values depend on the operating states of the
CPU and the supply voltage of the analog module
• The behavior of the analog modules depending on where the analog values lie
within the value range
• The effect of the operational limit of the analog module on the analog input and
output value, as illustrated by an example
4.5.1 Effect of Supply Voltage and Operating Mode
Effect of supply voltage and operating mode on the modules
The input and output values of the analog modules depend on the operating state
of the CPU and on the supply voltage of the module.
Table 4-38 Dependencies of the Analog Input/Output Values on the Operating State of the CPU and the
Supply Voltage L+
CPU Operating
State
POWER RUN L+ present
ON ON
L+ missing
POWER STOP L+ present
ON ON
L+ missing
POWER – L+ present
OFF OFF
L+ missing
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
Supply Vol- Input Value of the
tage L+ at Analog Input Module
Analog Mo-
dule
Measured value
7FFF until first conversion
H
following power-up or after
parameter assignment of the
module has been completed
Overflow value
Measured value
7FFF until first conversion
H
following power-up or after
parameter assignment of the
module has been completed
Overflow value
–
–
Analog Modules
Output Value of the
Analog Output Module
CPU values
Until the first conversion...
•
after power-up has been
completed, a signal of 0 mA
or 0 V is output.
•
after parameter
assignment has been
completed, the previous
value is output.
0 mA/0 V
Substitute value/last value
(default values: 0 mA/0 V) (default values: 0 mA/0 V)
0 mA/0 V
0 mA/0 V
0 mA/0 V
4-31