Siemens Simatic S7-1500 CPU 1512C-1 PN User Manual page 118

Parameters/address space
5.2 Address space of the digital on-board I/O
Value status (quality information, QI)
As of firmware version 2.0, the analog and digital on-board I/O support the value status as
diagnostics option. You activate the use of the value status in the hardware configuration of
STEP 7 (TIA Portal). Value status is deactivated by default. You can activate/deactivate the
value status of the digital on-board I/O for X11 and X12 independently of each other.
When you activate the value status, the input area of the digital on-board I/O (X11/X12)
contains four additional bytes, which provide the QI bits to the 16 digital input channels and
16 digital output channels. You access the QI bits through the user program.
Value status of input channels
Value status = 1 ("Good") indicates that the value of the assigned input at the terminal is
valid.
Value status = 0 ("Bad") indicates that no/or too little supply voltage L+ is applied at the
terminal and that the read value is therefore not valid.
Value status of output channels
The value status = 1 ("Good") indicates that the process value specified by the user program
is correctly output at the terminal.
The value status = 0 ("Bad") indicates that the process value output at the hardware output is
incorrect or the channel is used for technology functions.
Possible cause for value status = 0:
● The supply voltage L+ is missing at the terminals or is not sufficient
● Outputs are inactive (for example, CPU in STOP)
● Technology functions (HSC, PWM or PTO) use the channel
Note
Behavior of the value status at the output channels for technology functions
The output channels return the value status 0 ("Bad") when a technology channel (HSC,
PWM or PTO) is used. It does not matter in this context whether the output value is incorrect
or not.
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CPU 1512C-1 PN (6ES7512-1CK01-0AB0)
Manual, 12/2017, A5E40898741-AA