CPU 72x
24.05.2019
page 21
LED CAN2
LED CAN2 displays the status of CAN communication in the CPU 723-T on the second
CAN bus.
LED status
Meaning
off
CAN 2 not active
green on
CAN 2 no error, normal operating status
green flashing
Strongly disturbed data-transfer. The warning limit has been
reached. CAN communication conditionally possible.
red on
The CAN bus CAN 2 is in 'BUS OFF' state.
CAN communication is no longer possible.
The CAN controller has switched off.
LED ERR
LED ERR displays the error status on the CPU 725-LT/LTH and on the CPU 727-T/TH.
LED status
Meaning
off
No error
red on
The Watch-Dog-Reset is occurred
red flashing
Fatal error
The decentralized processor modules are trouble resistant according the IEC 61131
standards.
If other types of problems occur, the comportment of the CPU 72x is as follows:
1.6.2
Power Supply Breakdown (UC)
A powerfail is triggered if the supply voltage UC falls below the powerfail threshold U
PF
.
Powerfail Threshold in
the
Versions…
CPU 72x-T/LT
CPU 72x-TH/LTH
Powerfail threshold (U
PF
)
typ.
16 Vdc
17 Vdc
The CPUs accept a power interruption of 10
ms (according IEC 61131-2 PS2)
without any consequences.
If the supply voltage UC drops below 17 Vdc and the internal logic supply UL is still higher
as 4.65 Vdc, then all outputs are switched off and the CPU waits, until the internal logic
supply UL drops below 4.65 Vdc
. The application is not executed anymore and the ‘ERR’-
LED blinks. The application will only continue to work after a reset (UL < 4.65 Vdc).
When the internal logic supply UL will underpass UL 4.65 Vdc, a reset is released.
1.6.3
Overvoltage (UC and US)
The CPUs are protected against overvoltage peaks according the IEC 61131 standards. In
cases that the supply voltage is continuously higher than indicated in the technical data, a
destruction of the unit cannot be excluded.
