Siemens SINUMERIK 840Di Function Manual page 1233

M decoder
M functions can be used to transfer both switching commands and fixed point values.
Decoded dynamic signals are output to the CHANNEL DB interface for standard M functions
(range M00 - M99); signal length = 1 cycle time.
G group decoders
In the case of G functions sent by the NCK, the related groups are decoded and the current
G number is entered in the corresponding interface byte of the CHANNEL DB, i.e., all active
G functions are entered in the channel DBs. The entered G functions are retained even after
the NC program has terminated or aborted.
Note
During system start-up, all G group bytes are initialized with the value "0".
M, S, F distributor
The M, S, F, distributor is used to enter spindle-specific M words M(1...6)=[3,4,5], S words
and F words for axial feeds in the appropriate spindle and axis data blocks. The criterion for
distribution is the extended address, which is passed to the PLC for M words, S words and
axial F words.
MCP signal transmission
On the 840 D, depending on the bus connection, MCP signals are transmitted to the
parameterized I/O areas either directly to the PLC or indirectly via an internal procedure
using the basic program.
User messages
The acquisition and processing of the user error and operational messages is performed by
an FC in the basic program.
PLC Basic Program Solution Line (P3 sl)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.7 Structure and functions of the basic program
Detailed Description
2-39