Output Of The Scaling Result; Error Response - Siemens Simatic Manual

Fail-safe function blocks for storage and retrieval machines
Note
The permissible value ranges of the individual inputs should be taken from the
table describing the inputs.
Note
It is mandatory that this block is called with a dedicated instance DB, it is not
permissible to call it as multi-instance.
3.3.3.2

Output of the scaling result

14. Inputs OUT1_SCALE_DINT/OUT2_SCALE_DINT should be interconnected with the corre-
sponding outputs OUT1/OUT2 of block SCALE_DINT in the standard program using bit
memory words.
15. Internally, the block checks as to whether scale value transferred via these two inputs is plau-
sible, i.e. whether after decoding, the identical value was transferred.
16. When this is the case, then this value is output at OUT and SCALE_OK signals that scaling is
error-free using a 1 signal.
17. If an error occurs for the scaling itself, or for data transfer between the standard and the F part
of the scaling, then SCALE_OK is set to 0, and the last valid value is output at OUT.
3.3.3.3

Error response

18. The block does not have to be acknowledged. A value that has been identified as being invalid
at OUT is flagged using a 0 signal at SCALE_OK; it must be ensured that the system goes in-
to a safe state by using a suitable logic circuit.
19. A possible logic circuit in this case is to logically combined output SCALE_OK with input
POSx_VALID at block F_SAFE_POS.
As soon as an invalid value is available at OUT, the block F_SAFE_POS now responds in a
safety-related way by withdrawing POS_VALID; this signal is not automatically set again using
SCALE_OK.
The behavior of the ASRS block package is such that block F_SCALE_DINT is not required, if
the encoder directly supplies the value in the SLU unit.
Also refer to Chapter 0.
Safety notes and instructions
It must be carefully ensured that the machine does not automatically restart after
a 1->0->1 change at SCALE_OK by suitably interconnecting output SCALE_OK
in the user program.
S7-Distributed Safety/SIMATIC Safety - fail-safe function blocks for storage and retrieval machines
- 3-22 -