Siemens Simatic S7-300 - Page 237

Analog Modules
4-31
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
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
Supply Vol-
tage L+ at
Analog Mo-
dule
Input Value of the
Analog Input Module
Output Value of the
Analog Output Module
POWER
ON
RUN L+ present Measured value CPU values
ON
7FFF
H
until first conversion
following power-up or after
parameter assignment of the
module has been completed
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.
L+ missing Overflow value 0 mA/0 V
POWER
ON
STOP L+ present Measured value Substitute value/last value
(default values: 0 mA/0 V)
ON
7FFF
H
until first conversion
following power-up or after
parameter assignment of the
module has been completed
(default values: 0 mA/0 V)
L+ missing Overflow value 0 mA/0 V
POWER
OFF
– L+ present – 0 mA/0 V
OFF
L+ missing – 0 mA/0 V