Siemens SINUMERIK 840D sl Function Manual page 1654

Z1: NC/PLC interface signals
19.12 Feeds (V1)
DB21, ...
DBB4 Feedrate override
Signal state 1 or The feedrate override can be defined via the PLC in binary or Gray coding.
edge change
With binary coding, the feed value is interpreted in %.
0 → 1
0% to 200% feed changes are possible, in accordance with the binary value in the byte.
The following permanent assignment applies:
Binary values > 200 are limited to 200%.
The machine data:
MD12100 $MN_OVR_FACTOR_LIMIT_BIN (limit for binary-coded override switch)
can be used to additionally limit the maximum feedrate override.
In gray coding, the following codes are assigned to the individual switch settings:
1654
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions