Siemens Simatic S7-1500 CPU 1512C-1 PN User Manual page 115

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.
When you activate the value status, the input area of the analog on-board I/O contains two
additional bytes, which provide the QI bits to the five analog input channels and two analog
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 the read value is not valid.
Possible cause for value status = 0:
● a channel has been deactivated
● a measured value was not updated after a parameter change
● a measured value is outside the low/high measuring range (overflow/underflow)
● Wire break has occurred (only for the "Voltage" measurement type in the measuring
range "1 to 5 V" and for the "Current" measurement type in the measuring range "4 to
20 mA")
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.
Possible cause for value status = 0:
● a channel has been deactivated
● Outputs are inactive (for example, CPU in STOP)
● An output value is outside the lower/upper measuring range (overflow/underflow)
● Wire break has occurred (only for the "Current" output type)
● Short-circuit has occurred (only for the "Voltage" output type)
CPU 1512C-1 PN (6ES7512-1CK01-0AB0)
Manual, 12/2017, A5E40898741-AA
Parameters/address space
5.1 Address space of the analog on-board I/O
115