Siemens SIMATIC S7 F Manual page 204

Fail-Safe Blocks
8.2.3 F_CH_AI
Function
The block reads the analog non-linearized value of the input channel whose
symbolic name is linked to the input VALUE from the associated F module driver
(F_M_AIx). The F module driver has read the non-linearized value via a safety
frame from the analog input module (or possibly a module that is redundant to this
one). The connection to the associated F module driver (F_M_AIx) is automatically
established by means of the interconnection at the input CHADDR.
If the non-linearized value is valid, it is adapted to its physical size and made
available at the output V as a process value.
If the non-linearized value is invalid, a substitute value or the last valid value is
output at the output V, depending on the parameterization. For the reintegration of
a process value after an error is corrected, a user acknowledgment is required
depending on the parameterization and error type.
Alternatively, a simulation value can be output at the output V.
For the process value at the output V, a value status (quality code) is generated at
the output QUALITY that can take on the following states:
State
Valid value
Simulation value
Substitute value
Last valid value
I/Os
Inputs:
8-16
Quality Code
16#80
16#60
16#48
16#44
Name Data Type Explanation
ADDR_CODE DWORD
CHADDR F_WORD
VALUE WORD
VHRANGE F_REAL
VLRANGE F_REAL
CH_F_ON F_BOOL
CH_F_HL F_REAL
CH_F_LL F_REAL
SIM_V F_REAL
Address code for VALUE
interconnection
Address of the channel in the F
module driver
Must be interconnected with the
symbolic address of the channel
from HWCONFIG across the
margin of the chart
Upper limit of the process value
Lower limit of the process value
1=activate limit-value monitoring
Overrange limit of the input value
(mA)
Underrange limit of the input value
(mA)
Simulation value
Default
Supplied
automatically
Interconnected
automatically
0
0.0
0.0
0
0.0
0.0
0.0
Fail-Safe Systems
A5E00085588-03