Siemens SIMATIC S7 F Manual page 100

Programming
Drivers for the F-I/Os in Standard Mode
If you use the F-I/Os in standard mode, you can use the standard channel drivers
from the PCS 7 Driver Blocks library.
Rules for F-Driver Blocks
•
The VALUE I/O of the F channel driver must be interconnected with the
symbolic address of the channel. In the case of redundant channels, the
VALUE I/O must be interconnected with the symbolic address of the channel
with the lower address .
•
A fail-safe signal on the ACK_REI input of each channel driver is required to
reintegrate an input or output channel. The signal must come from a fail-safe
digital input module or – via the F_QUITES F block – from an ES or OS.
•
Sequence: See Defining the Run Sequence.
Prerequisite
Symbolic names: Enter a symbolic name for each channel used. You must
allocate this name to the VALUE I/O of the associated F channel driver. We
recommend, for the sake of clarity, that you also enter the unused channels in the
symbol table as reserved or not used.
Procedure
When working with F-driver blocks, proceed as follows:
1. Insert the correct F channel driver for each configured input/output channel.
You only have to insert one F channel driver for each pair of redundant
channels.
2. Interconnect the VALUE I/O in each F channel driver with the symbolic name
of the associated channel. This step is required for all F channel drivers
placed. In the case of redundant modules, interconnect the VALUE I/O with the
lower channel address.
3. Interconnect the following with the required signals:
- the I inputs of the F channel drivers F_CH_DO
- the Q outputs of the F channel drivers F_CH_DI
- the V outputs of the F channel drivers F_CH_AI
These I/Os are F_BOOL or F_REAL types and should only be interconnected with I/Os of
the same type belonging to other fail-safe blocks.
4. Set the relevant ACK_NEC input to "1" if user acknowledgment is required with
automatic reintegration of the channel. The ACK_NEC input is preset with "0"
(optional, see "Passivation and Reintegration").
5. Optional: Evaluate the ACK_REQ output in the standard program or on the OS
to find out if user acknowledgment is required.
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Fail-Safe Systems
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