Siemens SIMATIC NET CP 343-2 Manual page 132

Technical description
1.10 AS-Interface operation with 24 V voltage (AS-i Power24V)
NOTICE
Voltage lower than 22.5 V on the AS-Interface
If the voltage on the AS-Interface is less than 22.5 V (+/-1 V),
 the CP 343−2 / CP 343−2 P generates the message "AS-i POWER FAIL" (APF) when
 halts operation of the AS-Interface network.
The slaves connected to the AS-Interface network shut down automatically in response to
undervoltage.
In order to ensure fault-free operation under these conditions, voltage monitoring must be
deactivated!
Voltage monitoring is activated in the delivery state and the
CP 343-2 / CP 343-2 P module is thus preset for operation on a 30 V supply voltage.
Checking the setting of voltage monitoring (only on 6GK7 343-2AH01-0XA0 and
6GK7 343-2AH11-0XA0, product version 02):
Step
1: Install the CP as described in Section 2.2.
2: Switch the power supply to the SIMATIC station off and
then on again.
3: Check the status of the voltage monitoring by reading the
LED display.
Checking the setting for voltage monitoring
6
voltage monitoring is activated (setting in delivery state) and
Meaning
The CP performs a self-test when it powers up. All the LEDs
on the CP light up while it is powering up. Then the LEDs go
out.
There are two different cases:
Voltage monitoring is activated (setting in delivery state):

The LEDs immediately indicate the operating state
described in Section 1.5
Voltage monitoring is deactivated (for AS-i Power24V

operation): The two LEDs "APF" and "0" flash for about
2 s, the LEDs then display the operating state described
in Section 1.5.
CP 343-2/CP 343-2 P AS-Interface Master for SIMATIC S7
Supplement to Operating Manual, 08/2010, A5E03006584020A-01